U.S. patent number 9,648,254 [Application Number 14/664,754] was granted by the patent office on 2017-05-09 for compact light sensor.
This patent grant is currently assigned to Hypermed Imaging, Inc.. The grantee listed for this patent is Hypermed Imaging, Inc.. Invention is credited to Mark Anthony Darty, Peter Meenen, Michael Tilleman, Dmitry Yudovsky.
United States Patent |
9,648,254 |
Darty , et al. |
May 9, 2017 |
Compact light sensor
Abstract
Provided are methods and systems for concurrent imaging at
multiple wavelengths. In one aspect, a hyperspectral/multispectral
imaging device includes a lens configured to receive light
backscattered by an object, a plurality of photo-sensors, a
plurality of bandpass filters covering respective photo-sensors,
where each bandpass filter is configured to allow a different
respective spectral band to pass through the filter, and a
plurality of beam splitters in optical communication with the lens
and the photo-sensors, where each beam splitter splits the light
received by the lens into a plurality of optical paths, each path
configured to direct light to a corresponding photo-sensor through
the bandpass filter corresponding to the respective
photo-sensor.
Inventors: |
Darty; Mark Anthony
(Collierville, TN), Tilleman; Michael (Brookline, MA),
Meenen; Peter (Cane Ridge, TN), Yudovsky; Dmitry (Los
Angeles, CA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Hypermed Imaging, Inc. |
Memphis |
TN |
US |
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Assignee: |
Hypermed Imaging, Inc.
(Memphis, TN)
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Family
ID: |
54143278 |
Appl.
No.: |
14/664,754 |
Filed: |
March 20, 2015 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20150271380 A1 |
Sep 24, 2015 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61969039 |
Mar 21, 2014 |
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62090302 |
Dec 10, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01J
3/10 (20130101); G01J 3/108 (20130101); G01J
3/0291 (20130101); G01J 3/0272 (20130101); G01J
3/0294 (20130101); H04N 5/2256 (20130101); H04N
5/332 (20130101); G01J 3/0208 (20130101); G01J
3/0289 (20130101); G01J 3/0278 (20130101); H04N
5/2354 (20130101); G01J 3/0205 (20130101); G01J
3/0283 (20130101); H04N 5/2254 (20130101); G01J
3/36 (20130101); G01J 3/2823 (20130101); G06T
2207/10016 (20130101); G01J 2003/106 (20130101); G01J
2003/2826 (20130101); G01J 2003/1213 (20130101) |
Current International
Class: |
G01N
21/25 (20060101); H04N 5/33 (20060101); G01J
3/28 (20060101); G01J 3/02 (20060101); H04N
5/225 (20060101); H04N 5/235 (20060101) |
Field of
Search: |
;356/419 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2359745 |
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Aug 2011 |
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EP |
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WO 2008-100582 |
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Aug 2008 |
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WO |
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WO 2011-070357 |
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Jun 2011 |
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WO |
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Primary Examiner: Ayub; Hina F
Attorney, Agent or Firm: Lovejoy; Brett A. Antczak; Andrew
J. Morgan, Lewis & Bockius, LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATION
This application claims priority to U.S. Provisional Patent
Application No. 61/969,039, filed Mar. 21, 2014, and U.S.
Provisional Patent Application No. 62/090,302, filed Dec. 10, 2014,
the disclosures of which are hereby incorporated by reference
herein in their entireties for all purposes.
Claims
What is claimed is:
1. An imaging device, comprising: a lens disposed along an optical
axis and configured to receive light; a plurality of pixel array
photo-sensors; an optical path assembly comprising a plurality of
beam splitters in optical communication with the lens and the
plurality of pixel array photo-sensors; and a plurality of
multi-bandpass filters, wherein each respective multi-bandpass
filter in the plurality of multi-bandpass filters covers a
corresponding pixel array photo-sensor in the plurality of pixel
array photo-sensors thereby selectively allowing a different
corresponding spectral band of light, from the light received by
the lens and split by the plurality of beam splitters, to pass
through to the corresponding pixel array photo-sensor; wherein each
respective beam splitter in the plurality of beam splitters is
configured to split the light received by the lens into at least
two optical paths, a first beam splitter in the plurality of beam
splitters is in direct optical communication with the lens and a
second beam splitter in the plurality of beam splitters is in
indirect optical communication with the lens through the first beam
splitter, and the plurality of beam splitters collectively split
light received by the lens into a plurality of optical paths,
wherein each respective optical path in the plurality of optical
paths is configured to direct light to a corresponding pixel array
photo-sensor in the plurality of pixel array photo-sensors through
the respective multi-bandpass filter covering the corresponding
pixel array photo-sensor.
2. The imaging device of claim 1, wherein the plurality of
multi-bandpass filters are dual bandpass filters.
3. The imaging device of claim 1, further comprising a first light
source and a second light source, wherein the first light source
and the second light source are configured to shine light so that a
portion of the light is backscattered by an object and received by
the lens.
4. The imaging device of claim 3, wherein the first light source
emits light that is substantially limited to a first spectral
range, and the second light source emits light that is
substantially limited to a second spectral range.
5. The imaging device of claim 4, wherein the first light source is
a first multi-spectral light source covered by a first bandpass
filter, wherein the first bandpass filter substantially blocks all
light emitted by the first light source other than the first
spectral range, and the second light source is a second
multi-spectral light source covered by a second bandpass filter,
wherein the second bandpass filter substantially blocks all light
emitted by the second light source other than the second spectral
range.
6. The imaging device of claim 5, wherein the first multi-spectral
light source is a first white light emitting diode covered by the
first bandpass filter and the second multi-spectral light source is
a second white light emitting diode covered by the second bandpass
filter.
7. The imaging device of claim 4, wherein each respective
multi-bandpass filter in the plurality of multi-bandpass filters is
configured to selectively allow light corresponding to either of
two discrete spectral bands to pass through to the corresponding
pixel array photo-sensor.
8. The imaging device of claim 7, wherein: a first of the two
discrete spectral bands corresponds to a first spectral band that
is represented in the first spectral range and not in the second
spectral range; and a second of the two discrete spectral bands
corresponds to a second spectral band that is represented in the
second spectral range and not in the first spectral range.
9. The imaging device of claim 7, wherein the two discrete bands of
a multi-bandpass filter in the plurality of multi-bandpass filters
are separated by at least 60 nm.
10. The imaging device of claim 4, wherein the first spectral range
is substantially non-overlapping with the second spectral
range.
11. The imaging device of claim 4, wherein the first spectral range
is substantially contiguous with the second spectral range.
12. The imaging device of claim 4, wherein the first spectral range
comprises 520 nm, 540 nm, 560 nm and 640 nm wavelength light and
does not include 580 nm, 590 nm, 610 nm and 620 nm wavelength
light, and the second spectral range comprises 580 nm, 590 nm, 610
nm and 620 nm wavelength light and does not include 520 nm, 540 nm,
560 nm and 640 nm wavelength light.
13. The imaging device of claim 4, further comprising a controller
configured to capture a plurality of images from the plurality of
pixel array photo-sensors by performing a method including: (A)
illuminating the object a first time using the first light source;
(B) capturing a first set of images with the plurality of pixel
array photo-sensors during the illuminating (A), wherein the first
set of images includes, for each respective pixel array
photo-sensor in the plurality of pixel array photo-sensors, an
image corresponding to a first spectral band transmitted by the
corresponding multi-bandpass filter, wherein the light falling
within the first spectral range includes light falling within the
first spectral band of each multi-bandpass filter in the plurality
of multi-bandpass filters; (C) extinguishing the first light
source; (D) illuminating the object a second time using the second
light source; and (E) capturing a second set of images with the
plurality of pixel array photo-sensors during the illuminating (D),
wherein the second set of images includes, for each respective
pixel array photo-sensor in the plurality of pixel array
photo-sensors, an image corresponding to a second spectral band
transmitted by the corresponding multi-bandpass filter, wherein the
light falling within the second spectral range includes light
falling within the second spectral band of each multi-bandpass
filter in the plurality of multi-bandpass filters.
14. The imaging device of claim 13, wherein each respective pixel
array photo-sensor in the plurality of pixel array photo-sensors is
a pixel array that is controlled by a corresponding shutter
mechanism that determines an image integration time for the
respective pixel array photo-sensor, and a first pixel array
photo-sensor in the plurality of pixel array photo-sensors is
independently associated with a first integration time for use
during the capturing (B) and a second integration time for use
during the capturing (E), wherein the first integration time is
independent of the second integration time.
15. The imaging device of claim 13, wherein each respective pixel
array photo-sensor in the plurality of pixel array photo-sensors is
a pixel array that is controlled by a corresponding shutter
mechanism that determines an image integration time for the
respective pixel array photo-sensor, a duration of the illuminating
(A) is determined by a first maximum integration time associated
with the plurality of pixel array photo-sensors during the
capturing (B), wherein an integration time of a first pixel array
photo-sensor in the plurality of pixel array photo-sensors is
different than an integration time of a second pixel array
photo-sensor in the plurality of pixel array photo-sensors during
the capturing (B), a duration of the illuminating (D) is determined
by a second maximum integration time associated with the plurality
of pixel array photo-sensors during the capturing (E), wherein an
integration time of the first pixel array photo-sensor is different
than an integration time of the second pixel array photo-sensor
during the capturing (E), and the first maximum integration time is
different than the second maximum integration time.
16. The imaging device of claim 13, wherein each image in the
plurality of images is a multi-pixel image of a location on the
object, the method further comprising: (F) combining each image in
the plurality of images, on a pixel by pixel basis, to form a
composite image.
17. The imaging device of claim 13, wherein, the imaging device is
portable and powered independent of a power grid during the
illuminating (A) and the illuminating (D), the first light source
provides at least 80 watts of illuminating power during the
illuminating (A), the second light source provides at least 80
watts of illuminating power during the illuminating (D), and the
imaging device further comprises a capacitor bank in electrical
communication with the first light source and the second light
source, wherein a capacitor in the capacitor bank has a voltage
rating of at least 2 volts and a capacitance rating of at least 80
farads.
18. The imaging device of claim 13, wherein the imaging device is
portable and electrically independent of a power grid during the
illuminating (A) and the illuminating (D), and wherein the
illuminating (A) occurs for less than 300 milliseconds and the
illuminating (D) occurs for less than 300 milliseconds.
19. The imaging device of claim 3, wherein the first light source
is in a first lighting assembly and the second light source is in a
second lighting assembly separate from the first lighting
assembly.
20. The imaging device of claim 1, further comprising a plurality
of beam steering elements, each respective beam steering element
configured to direct light in a respective optical path to a
respective pixel array photo-sensor, of the plurality of pixel
array photo-sensors, corresponding to the respective optical
path.
21. The imaging device of claim 20, wherein each one of a first
subset of the plurality of beam steering elements is configured to
direct light in a first direction that is perpendicular to the
optical axis, and each one of a second subset of the plurality of
beam steering elements is configured to direct light in a second
direction that is perpendicular to the optical axis and opposite to
the first direction.
22. The imaging device of claim 1, wherein each beam splitter in
the plurality of beam splitters exhibits a ratio of light
transmission to light reflection of about 50:50.
23. The imaging device of claim 22, wherein the beam splitters are
wavelength-independent beam splitters.
24. The imaging device of claim 1, further comprising: a first
circuit board positioned on a first side of the optical path
assembly, wherein a first pixel array photo-sensor and a third
pixel array photo-sensor in the plurality of pixel array
photo-sensors are coupled to the first circuit board; and a second
circuit board positioned on a second side of the optical path
assembly opposite to the first side, wherein the second circuit
board is substantially parallel with the first circuit board,
wherein a second pixel array photo-sensor and a fourth pixel array
photo-sensor in the plurality of pixel array photo-sensors are
coupled to the second circuit board, and wherein: the first beam
splitter is configured to split light received from the lens into a
first optical path and a second optical path, wherein the first
optical path is substantially collinear with the optical axis, and
the second optical path is substantially perpendicular to the
optical axis, the second beam splitter is configured split light
from the first optical path into a third optical path and a fourth
optical path, wherein the third optical path is substantially
collinear with the first optical path, and the fourth optical path
is substantially perpendicular to the optical axis, a third beam
splitter in the plurality of beam splitters is configured to split
light from the second optical path into a fifth optical path and a
sixth optical path, wherein the fifth optical path is substantially
collinear with the second optical path, and the sixth optical path
is substantially perpendicular to the second optical path, and
wherein the optical path assembly further comprises: a first beam
steering element configured to deflect light from the third optical
path perpendicular to the third optical path and onto the first
pixel array photo-sensor coupled to the first circuit board, a
second beam steering element configured to deflect light from the
fourth optical path perpendicular to the fourth optical path and
onto the second pixel array photo-sensor coupled to the second
circuit board, a third beam steering element configured to deflect
light from the fifth optical path perpendicular to the fifth
optical path and onto the third pixel array photo-sensor coupled to
the first circuit board, and a fourth beam steering element
configured to deflect light from the sixth optical path
perpendicular to the sixth optical path and onto the fourth pixel
array photo-sensor coupled to the second circuit board.
25. The imaging device of claim 24, wherein a first multi-bandpass
filter in the plurality of multi-bandpass filters is positioned in
the third optical path between the first beam splitter and the
first pixel array photo-sensor, a second multi-bandpass filter in
the plurality of multi-bandpass filters is positioned in the fourth
optical path between the second beam splitter and the second pixel
array photo-sensor, a third multi-bandpass filter in the plurality
of multi-bandpass filters is positioned in the fifth optical path
between the third beam splitter and the third pixel array
photo-sensor, and a fourth multi-bandpass filter in the plurality
of multi-bandpass filters is positioned in the sixth optical path
between the fourth beam splitter and the fourth pixel array
photo-sensor.
26. The imaging device of claim 24, further comprising a polarizing
filter disposed along the optical axis.
27. The imaging device of claim 26, wherein the polarizing filter
is adjacent to the lens and before the first beam splitter along
the optical axis.
28. The imaging device of claim 24, wherein the first beam steering
element is a folding prism.
29. The imaging device of claim 24, wherein each respective beam
splitter and each respective beam steering element is oriented
along substantially the same plane.
30. The imaging device of claim 24, wherein the first beam
splitter, the second beam splitter, and the third beam splitter
each exhibits a ratio of light transmission to light reflection of
about 50:50.
Description
TECHNICAL FIELD
The present disclosure generally relates to spectroscopy, such as
hyperspectral spectroscopy, and in particular, to systems, methods
and devices enabling a compact imaging device.
BACKGROUND
Hyperspectral (also known as "multispectral") spectroscopy is an
imaging technique that integrates multiple images of an object
resolved at different spectral bands (e.g., ranges of wavelengths)
into a single data structure, referred to as a three-dimensional
hyperspectral data cube. Data provided by hyperspectral
spectroscopy is often used to identify a number of individual
components of a complex composition through the recognition of
spectral signatures of the individual components of a particular
hyperspectral data cube.
Hyperspectral spectroscopy has been used in a variety of
applications, ranging from geological and agricultural surveying to
surveillance and industrial evaluation. Hyperspectral spectroscopy
has also been used in medical applications to facilitate complex
diagnosis and predict treatment outcomes. For example, medical
hyperspectral imaging has been used to accurately predict viability
and survival of tissue deprived of adequate perfusion, and to
differentiate diseased (e.g., cancerous or ulcerative) and ischemic
tissue from normal tissue.
However, despite the great potential clinical value of
hyperspectral imaging, several drawbacks have limited the use of
hyperspectral imaging in the clinic setting. In particular, medical
hyperspectral instruments are costly because of the complex optics
and computational requirements conventionally used to resolve
images at a plurality of spectral bands to generate a suitable
hyperspectral data cube. Hyperspectral imaging instruments can also
suffer from poor temporal and spatial resolution, as well as low
optical throughput, due to the complex optics and taxing
computational requirements needed for assembling, processing, and
analyzing data into a hyperspectral data cube suitable for medical
use.
Thus, there is an unmet need in the field for less expensive and
more rapid means of hyperspectral/multispectral imaging and data
analysis. The present disclosure meets these and other needs by
providing methods and systems for concurrently capturing images at
multiple wavelengths.
SUMMARY
Various implementations of systems, methods, and devices within the
scope of the appended claims each have several aspects, no single
one of which is solely responsible for the desirable attributes
described herein. Without limiting the scope of the appended
claims, some prominent features are described herein. After
considering this discussion, and particularly after reading the
section entitled "Detailed Description" one will understand how the
features of various implementations are used to enable a
hyperspectral imaging device capable of producing a
three-dimensional hyperspectral data cube using a plurality of
photo-sensor chips (e.g., CDD, CMOS, etc) suitable for use in a
number for applications, and in particular, for medical use.
First Aspect.
Various aspects of the present disclosure are directed to an
imaging device, including a lens disposed along an optical axis and
configured to receive light that has been emitted from a light
source and backscattered by an object, a plurality of
photo-sensors, a plurality of dual bandpass filters, each
respective dual bandpass filter covering a respective photo-sensor
of the plurality of photo-sensors and configured to filter light
received by the respective photo-sensor, wherein each respective
dual bandpass filter is be configured to allow a different
respective spectral band to pass through the respective dual
bandpass filter, and a plurality of beam splitters in optical
communication with the lens and the plurality of photo-sensors.
Each respective beam splitter is configured to split the light
received by the lens into at least two optical paths. A first beam
splitter in the plurality of beam splitters is in direct optical
communication with the lens and a second beam splitter in the
plurality of beam splitters is in indirect optical communication
with the lens through the first beam splitter. The plurality of
beam splitters collectively split the light received by the lens
into a plurality of optical paths. Each respective optical path in
the plurality of optical paths is configured to direct light to a
corresponding photo-sensor in the plurality of photo-sensors
through the dual bandpass filter corresponding to the respective
photo-sensor.
In some embodiments, the imaging device further includes at least
one light source having at least a first operating mode and a
second operating mode. In the first operating mode, the at least
one light source emits light substantially within a first spectral
range, and in the second operating mode, the at least one light
source emits light substantially within a second spectral
range.
In some embodiments, each of the plurality of bandpass filters is
configured to allow light corresponding to either of two discrete
spectral bands to pass through the filter. In some embodiments, a
first of the two discrete spectral bands corresponds to a first
spectral band that is represented in the first spectral range and
not in the second spectral range, and a second of the two discrete
spectral bands corresponds to a second spectral band that is
represented in the second spectral range and not in the first
spectral range.
In some embodiments, the first spectral range is substantially
non-overlapping with the second spectral range. In some
embodiments, the first spectral range is substantially contiguous
with the second spectral range.
In some embodiments, the at least two optical paths from a
respective beam splitter in the plurality of beam splitters are
substantially coplanar.
In some embodiments, the imaging device further includes a
plurality of beam steering elements, each respective beam steering
element configured to direct light in a respective optical path to
a respective photo-sensor corresponding to the respective optical
path. In some embodiments, at least one of the plurality of beam
steering elements is configured to direct light perpendicular to
the optical axis of the lens. In some embodiments, each one of a
first subset of the respective beam steering elements is configured
to direct light in a first direction that is perpendicular to the
optical axis of the lens, and each one of a second subset of the
respective beam steering elements is configured to direct light in
a second direction that is perpendicular to the optical axis of the
lens and opposite to the first direction.
In some embodiments, a sensing plane of each of the plurality of
photo-sensors is substantially perpendicular to the optical axis of
the lens.
In some embodiments, the imaging device further includes a
polarizer in optical communication with the at least one light
source, and a polarization rotator. The polarizer is configured to
receive light from the at least one light source and project a
first portion of the light from the at least one light source onto
the object. The first portion of the light is polarized in a first
manner. The polarizer is further configured to project a second
portion of the light from the at least one light source onto the
polarization rotator. The second portion of the light is polarized
in a second manner, other than the first manner. In some
embodiments, the polarization rotator is configured to rotate the
polarization of the second portion of the light from the second
manner to the first manner, and project the second portion of the
light, polarized in the first manner, onto the object. In some
embodiments, the first manner is p-polarization and the second
manner is s-polarization. In some embodiments, the first manner is
s-polarization and the second manner is p-polarization.
In some embodiments, the imaging device further includes a
controller configured to capture a plurality of images from the
plurality of photo-sensors by performing a method including using
the at least one light source to illuminate the object with light
falling within the first spectral range and capturing a first set
of images with the plurality of photo-sensors. In such embodiments,
the first set of images includes, for each respective photo-sensor,
an image corresponding to a first spectral band transmitted by the
corresponding dual bandpass filter, where the light falling within
the first spectral range includes light falling within the first
spectral band of each dual bandpass filter. The method further
comprises using the at least one light source to illuminate the
object with light falling within the second spectral range, and
capturing a second set of images with the plurality of
photo-sensors. In such embodiments, the second set of images
includes, for each respective photo-sensor, an image corresponding
to a second spectral band transmitted by the corresponding dual
bandpass filter, where the light falling within the second spectral
range includes light falling within the second spectral band of
each dual bandpass filter.
In some embodiments, the lens has a fixed focus distance, and the
imaging device further includes a first projector configured to
project a first portion of a shape onto the object, and a second
projector configured to project a second portion of the shape onto
the object, where the first portion of the shape and the second
portion of the shape are configured to converge to form the shape
when the lens is positioned at a predetermined distance from the
object. This predetermined distance corresponds to the focal
distance of the lens. In some embodiments, the shape indicates a
portion of the object that will be imaged by the plurality of
photo-sensors when an image is captured with the imaging device. In
some embodiments, the shape is selected from the group consisting
of: a rectangle; a square; a circle; and an oval. In some
embodiments, the shape is any two-dimensional closed form shape. In
some embodiments, the first portion of the shape is a first pair of
lines forming a right angle, and the second portion of the shape is
a second pair of lines forming a right angle, where the first
portion of the shape and the second portion of the shape are
configured to form a rectangle on the object when the imaging
device is positioned at a predetermined distance from the
object.
In some embodiments, each of the plurality of beam splitters
exhibits a ratio of light transmission to light reflection of about
50:50.
In some embodiments, at least one of the beam splitters in the
plurality of beam splitters is a dichroic beam splitter.
In some embodiments, at least the first beam splitter is a dichroic
beam splitter.
In some embodiments, in the first operating mode, the at least one
light source emits light substantially within a first spectral
range that includes at least two discontinuous spectral sub-ranges,
and in the second operating mode, the at least one light source
emits light substantially within a second spectral range.
In some embodiments, the first beam splitter is configured to
transmit light falling within a third spectral range and reflect
light falling within a fourth spectral range.
In some embodiments, the plurality of beam splitters includes the
first beam splitter, the second beam splitter, and a third beam
splitter. In some embodiments, the light falling within the third
spectral range is transmitted toward the second beam splitter, and
the light falling within the fourth spectral range is reflected
toward the third beam splitter.
In some embodiments, the second and the third beam splitters are
wavelength-independent beam splitters.
In some embodiments, the at least two discontinuous spectral
sub-ranges of the first spectral range include a first spectral
sub-range of about 450-550 nm, a second spectral sub-range of about
615-650 nm, and the second spectral range is about 550-615 nm.
In some embodiments, the third spectral range is about 585-650 nm,
and the fourth spectral range is about 450-585 nm.
In some embodiments, the third spectral range includes light
falling within both the first and the second spectral ranges, and
the fourth spectral range includes light falling within both the
first and the second spectral ranges.
In some embodiments, the first beam splitter is a plate dichroic
beam splitter or a block dichroic beam splitter.
In some embodiments, the first beam splitter, the second beam
splitter, and the third beam splitter are dichroic beam
splitters.
In some embodiments, in the first operating mode, the at least one
light source emits light substantially within a first spectral
range that includes at least two discontinuous spectral sub-ranges,
and in the second operating mode, the at least one light source
emit lights substantially within a second spectral range.
In some embodiments, the first beam splitter is configured to
transmit light falling within a third spectral range that includes
at least two discontinuous spectral sub-ranges and reflect light
falling within a fourth spectral range that includes at least two
discontinuous spectral sub-ranges.
In some embodiments, the plurality of beam splitters includes the
first beam splitter, the second beam splitter, and a third beam
splitter.
In some embodiments, the light falling within the third spectral
range is transmitted toward the second beam splitter, and the light
falling within the fourth spectral range is reflected toward the
third beam splitter.
In some embodiments, the second beam splitter is configured to
reflect light falling within a fifth spectral range that includes
at least two discontinuous spectral sub-ranges and transmit light
not falling within either of the at least two discontinuous
spectral sub-ranges of the fifth spectral sub-range.
In some embodiments, the third beam splitter is configured to
reflect light falling within a sixth spectral range that includes
at least two discontinuous spectral sub-ranges and transmit light
not falling within either of the at least two discontinuous
spectral sub-ranges of the sixth spectral sub-range.
In some embodiments, the at least two discontinuous spectral
sub-ranges of the first spectral range include a first spectral
sub-range of about 450-530 nm, and a second spectral sub-range of
about 600-650 nm, and the second spectral range is about 530-600
nm.
In some embodiments, the at least two discontinuous spectral
sub-ranges of the third spectral range include a third spectral
sub-range of about 570-600 nm, and a fourth spectral sub-range of
about 615-650 nm, and the at least two discontinuous spectral
sub-ranges of the fourth spectral range include a fifth spectral
sub-range of about 450-570 nm, and a sixth spectral sub-range of
about 600-615 nm.
In some embodiments, the at least two discontinuous spectral
sub-ranges of the fifth spectral range include a seventh spectral
sub-range of about 585-595 nm, and an eighth spectral sub-range of
about 615-625 nm.
In some embodiments, the at least two discontinuous spectral
sub-ranges of the sixth spectral range include a ninth spectral
sub-range of about 515-525 nm, and a tenth spectral sub-range of
about 555-565 nm.
In some embodiments, the first beam splitter, the second beam
splitter, and the third beam splitter are each either a plate
dichroic beam splitter or a block dichroic beam splitter.
In some embodiments, the at least one light source includes a first
set of light emitting diodes (LEDs) and a second set of LEDs, each
LED of the first set of LEDs transmits light through a first
bandpass filter configured to block light falling outside the first
spectral range and transmit light falling within the first spectral
range, and each LED of the second set of LEDs transmits light
through a second bandpass filter configured to block light falling
outside the second spectral range and transmit light falling within
the second spectral range.
In some embodiments, the first set of LEDs are in a first lighting
assembly and the second LEDs are in a second lighting assembly
separate from the first lighting assembly.
In some embodiments, the first set of LEDs and the second set of
LEDs are in a common lighting assembly.
Second Aspect.
Other aspects of the present disclosure are directed to an optical
assembly for an imaging device (e.g, a
hyper-spectral/multispectral), including a lens disposed along an
optical axis, an optical path assembly configured to receive light
from the lens, a first circuit board positioned on a first side of
the optical path assembly, and a second circuit board positioned on
a second side of the optical path assembly opposite to the first
side. The second circuit board is substantially parallel with the
first circuit board. The optical path assembly includes a first
beam splitter configured to split light received from the lens into
a first optical path and a second optical path. The first optical
path is substantially collinear with the optical axis. The second
optical path is substantially perpendicular to the optical axis. A
second beam splitter is adjacent to the first beam splitter. The
second beam splitter is configured to split light from the first
optical path into a third optical path and a fourth optical path.
The third optical path is substantially collinear with the first
optical path, and the fourth optical path is substantially
perpendicular to the optical axis. A third beam splitter is
adjacent to the first beam splitter. The third beam splitter is
configured to split light from the second optical path into a fifth
optical path and a sixth optical path. The fifth optical path is
substantially collinear with the second optical path, and the sixth
optical path is substantially perpendicular to the second optical
path. A first beam steering element is adjacent to the second beam
splitter and is configured to deflect light from the third optical
path perpendicular to the third optical path and onto a first
photo-sensor coupled to the first circuit board. A second beam
steering element is adjacent to the second beam splitter and is
configured to deflect light from the fourth optical path
perpendicular to the fourth optical path and onto a second
photo-sensor coupled to the second circuit board. A third beam
steering element is adjacent to the third beam splitter and is
configured to deflect light from the fifth optical path
perpendicular to the fifth optical path and onto a third
photo-sensor coupled to the first circuit board. A fourth beam
steering element is adjacent to the third beam splitter and is
configured to deflect light from the sixth optical path
perpendicular to the sixth optical path and onto a fourth
photo-sensor coupled to the second circuit board.
In some embodiments, the optical assembly further includes a
plurality of bandpass filters. The plurality of bandpass filters
includes a first bandpass filter positioned in the third optical
path between the second beam splitter and the first photo-sensor, a
second bandpass filter positioned in the fourth optical path
between the second beam splitter and the second photo-sensor, a
third bandpass filter positioned in the fifth optical path between
the third beam splitter and the third photo-sensor, and a fourth
bandpass filter positioned in the sixth optical path between the
third beam splitter and the fourth photo-sensor. Each respective
bandpass filter is configured to allow a different corresponding
spectral band to pass through the respective bandpass filter.
In some embodiments, at least one respective bandpass filter in the
plurality of bandpass filters is a dual bandpass filter.
In some embodiments, the optical assembly further includes a
polarizing filter disposed along the optical axis. In some
embodiments, the polarizing filter is adjacent to the lens and
before the first beam splitter along the optical axis.
In some embodiments, each respective beam steering element is a
mirror or prism. In some embodiments, each respective beam steering
element is a folding prism.
In some embodiments, each respective beam splitter and each
respective beam steering element is oriented along substantially
the same plane.
In some embodiments, each respective photo-sensor is flexibly
coupled to its corresponding circuit board.
In some embodiments, the first beam splitter, the second beam
splitter, and the third beam splitter each exhibit a ratio of light
transmission to light reflection of about 50:50.
In some embodiments, at least the first beam splitter is a dichroic
beam splitter.
In some embodiments, the first beam splitter is configured to
transmit light falling within a first spectral range and reflect
light falling within a second spectral range.
In some embodiments, the light falling within the first spectral
range is transmitted toward the second beam splitter, and the light
falling within the second spectral range is reflected toward the
third beam splitter.
In some embodiments, the second and the third beam splitters are
wavelength-independent beam splitters.
In some embodiments, the first beam splitter, the second beam
splitter, and the third beam splitter are dichroic beam
splitters.
In some embodiments, the first beam splitter is configured to
transmit light falling within a first spectral range that includes
at least two discontinuous spectral sub-ranges and reflect light
falling within a second spectral range that includes at least two
discontinuous spectral sub-ranges.
In some embodiments, the second beam splitter is configured to
reflect light falling within a third spectral range that includes
at least two discontinuous spectral sub-ranges and transmit light
not falling within either of the at least two discontinuous
spectral sub-ranges of the third spectral sub-range.
In some embodiments, the third beam splitter is configured to
reflect light falling within a fourth spectral range that includes
at least two discontinuous spectral sub-ranges and transmit light
not falling within either of the at least two discontinuous
spectral sub-ranges of the fourth spectral sub-range.
Third Aspect.
Other aspects of the present disclosure are directed to a lighting
assembly for an imaging (e.g., hyper-spectral/multispectral
imaging) device, including at least one light source, a polarizer
in optical communication with the at least one light source, and a
polarization rotator. The polarizer is configured to receive light
from the at least one light source and project a first portion of
the light from the at least one light source onto an object, where
the first portion of the light exhibits a first type of
polarization, and project a second portion of the light from the at
least one light source onto the polarization rotator, where the
second portion of the light exhibits a second type of polarization.
The polarization rotator is configured to rotate the polarization
of the second portion of the light from the second type of
polarization to the first type of polarization, and project the
light of the first type of polarization onto the object.
In some embodiments, the first type of polarization is
p-polarization and the second type of polarization is
s-polarization. In some embodiments, the first type of polarization
is s-polarization and the second type of polarization is
p-polarization.
In some embodiments, the at least one light source is one or more
light emitting diodes (LED).
In some embodiments, the at least one light source has two or more
operating modes, each respective operating mode in the two or more
operation modes including emission of a discrete spectral range of
light, where none of the respective spectral ranges of light
corresponding to an operating mode completely overlaps with any
other respective spectral range of light corresponding to a
different operating mode.
In some embodiments, at least 95% of all of the light received by
the polarizer from the at least one light source is illuminated
onto the object.
Fourth Aspect.
Another aspect of the present disclosure is directed to a method
for capturing an image (e.g., a hyper-spectral/multispectral image)
of an object, including at an imaging system including at least one
light source, a lens configured to receive light that has been
emitted from the at least one light source and backscattered by an
object, a plurality of photo-sensors, and a plurality of bandpass
filters. Each respective bandpass filter covers a respective
photo-sensor of the plurality of photo-sensors and configured to
filter light received by the respective photo-sensor. Each
respective bandpass filter is configured to allow a different
respective spectral band to pass through the respective bandpass
filter, illuminating the object with the at least one light source
according to a first mode of operation of the at least one light
source, capturing a first plurality of images, each of the first
plurality of images being captured by a respective one of the
plurality of photo-sensors, wherein each respective image of the
first plurality of images includes light having a different
respective spectral band.
Each of the plurality of bandpass filters is configured to allow
light corresponding to either of two discrete spectral bands to
pass through the filter. The method further includes, after
capturing the first plurality of images, illuminating the object
with the at least one light source according to a second mode of
operation of the at least one light source, capturing a second
plurality of images, each of the second plurality of images being
captured by a respective one of the plurality of photo-sensors,
wherein each respective image of the second plurality of images
includes light having a different respective spectral band, and the
spectral bands captured by the second plurality of images different
than the spectral bands captured by the first plurality of
images.
In some embodiments, the at least one light source includes a
plurality of light emitting diodes (LEDs).
In some embodiments, a first wavelength optical filter is disposed
along an illumination optical path between a first subset of LEDs
in the plurality of LEDs and the object, and a second wavelength
optical filter is disposed along an illumination optical path
between a second subset of LEDs in the plurality of LEDs and the
object. The first wavelength optical filter and the second
wavelength optical filter are configured to allow light
corresponding to different spectral bands to pass through the
respective filters.
In some embodiments, the plurality of LEDs include white
light-emitting LEDs. In some embodiments, the plurality of LEDs
include a first subset of LEDs configured to emit light
corresponding to a first spectral band of light and a second subset
of LEDs configured to emit light corresponding to a second spectral
band of light illuminating the object with the at least one light
source according to a first mode of operation consists of
illuminating the object with light emitted from the first subset of
LEDs, and illuminating the object with the at least one light
source according to a second mode of operation consists of
illuminating the object with light emitted from the second subset
of LEDs, where the wavelengths of the first spectral band of light
and the wavelengths of the second spectral band of light do not
completely overlap or do not overlap at all.
Fifth Aspect.
Another aspect of the present disclosure is directed to an imaging
device (e.g., hyper-spectral/multispectral imaging device),
including at least one light source having at least two operating
modes, a lens disposed along an optical axis and configured to
receive light that has been emitted from the at least one light
source and backscattered by an object, a plurality of
photo-sensors, a plurality of bandpass filters, each respective
bandpass filter covering a respective photo-sensor of the plurality
of photo-sensors and configured to filter light received by the
respective photo-sensor. Each respective bandpass filter is
configured to allow a different respective spectral band to pass
through the respective bandpass filter. The device further includes
one or more beam splitters in optical communication with the lens
and the plurality of photo-sensors. Each respective beam splitter
is configured to split the light received by the lens into a
plurality of optical paths. Each optical path is configured to
direct light to a respective photo-sensor through the bandpass
filter corresponding to the respective photo-sensor.
Sixth Aspect.
Another aspect of the present disclosure is directed to an imaging
device, including a lens disposed along an optical axis and
configured to receive light, a plurality of photo-sensors, an
optical path assembly including a plurality of beam splitters in
optical communication with the lens and the plurality of
photo-sensors, and a plurality of multi-bandpass filters (e.g.,
dual bandpass filters, triple bandpass filters, quad-bandpass
filters). Each respective multi-bandpass filter in the plurality of
multi-bandpass filters covers a corresponding photo-sensor in the
plurality of photo-sensors thereby selectively allowing a different
corresponding spectral band of light, from the light received by
the lens and split by the plurality of beam splitters, to pass
through to the corresponding photo-sensor. Each beam splitter in
the plurality of beam splitters is configured to split the light
received by the lens into at least two optical paths. A first beam
splitter in the plurality of beam splitters is in direct optical
communication with the lens. A second beam splitter in the
plurality of beam splitters is in indirect optical communication
with the lens through the first beam splitter. The plurality of
beam splitters collectively split light received by the lens into a
plurality of optical paths, wherein each respective optical path in
the plurality of optical paths is configured to direct light to a
corresponding photo-sensor in the plurality of photo-sensors
through the multi-bandpass filter corresponding to the respective
photo-sensor.
In a specific embodiment, the multi-bandpass filters are dual
bandpass filters. In some implementations, each respective optical
detector in the plurality of optical detectors (e.g., optical
detectors 112) is covered by a dual-band pass filter (e.g., filters
114).
In some implementations, each respective optical detector is
covered by a triple band pass filter, enabling use of a third light
source and collection of three sets of images at unique spectral
bands. For example, four optical detectors can collect images at up
to twelve unique spectral bands, when each detector is covered by a
triple band-pass filter.
In some implementations, each respective optical detector is
covered by a quad-band pass filter, enabling use of a fourth light
source and collection of four sets of images at unique spectral
bands. For example, four optical detectors can collect images at up
to sixteen unique spectral bands, when each detector is covered by
a quad band-pass filter. In yet other implementations, band pass
filters allowing passage of five, six, seven, or more bands each
can be used to collect larger sets of unique spectral bands.
In some embodiments, the imaging device also includes a first light
source and a second light source, wherein the first light source
and the second light source are configured to shine light so that a
portion of the light is backscattered by the object and received by
the lens.
In some embodiments, the first light source emits light that is
substantially limited to a first spectral range, and the second
light source emits light that is substantially limited to a second
spectral range.
In some embodiments, the first light source is a first
multi-spectral light source covered by a first bandpass filter,
wherein the first bandpass filter substantially blocks all light
emitted by the first light source other than the first spectral
range, and the second light source is a second multi-spectral light
source covered by a second bandpass filter, wherein the second
bandpass filter substantially blocks all light emitted by the
second light source other than the second spectral range.
In some embodiments, the first multi-spectral light source is a
first white light emitting diode and the second multi-spectral
light source is a second white light emitting diode.
In some embodiments, each respective dual bandpass filter in the
plurality of dual bandpass filters is configured to selectively
allow light corresponding to either of two discrete spectral bands
to pass through to the corresponding photo-sensor. In some
embodiments, a first of the two discrete spectral bands corresponds
to a first spectral band that is represented in the first spectral
range and not in the second spectral range, and a second of the two
discrete spectral bands corresponds to a second spectral band that
is represented in the second spectral range and not in the first
spectral range.
In some embodiments, the first spectral range is substantially
non-overlapping with the second spectral range.
In some embodiments, the first spectral range is substantially
contiguous with the second spectral range.
In some embodiments, the first spectral range comprises wavelengths
520 nm, 540 nm, 560 nm and 640 nm wavelength light, and the second
spectral range comprises of 580 nm, 590 nm, 610 nm and 620 nm
wavelength light.
In some embodiments, the at least two optical paths from a
respective beam splitter in the plurality of beam splitters are
substantially coplanar.
In some embodiments, the imaging device further includes a
plurality of beam steering elements, each respective beam steering
element configured to direct light in a respective optical path to
a respective photo-sensor, of the plurality of photo-sensors,
corresponding to the respective optical path. In some embodiments,
at least one of the plurality of beam steering elements is
configured to direct light perpendicular to the optical axis of the
lens. In some embodiments, each one of a first subset of the
plurality of beam steering elements is configured to direct light
in a first direction that is perpendicular to the optical axis, and
each one of a second subset of the plurality of beam steering
elements is configured to direct light in a second direction that
is perpendicular to the optical axis and opposite to the first
direction.
In some embodiments, a sensing plane of each of the plurality of
photo-sensors is substantially perpendicular to the optical
axis.
In some embodiments, the imaging device further includes a
controller configured to capture a plurality of images from the
plurality of photo-sensors by performing a method that includes
illuminating the object a first time using the first light source,
and capturing a first set of images with the plurality of
photo-sensors during the illumination. The first set of images
includes, for each respective photo-sensor in the plurality of
photo-sensors, an image corresponding to a first spectral band
transmitted by the corresponding multi-bandpass filter (e.g., dual
bandpass filter), where the light falling within the first spectral
range includes light falling within the first spectral band of each
multi-bandpass filter (e.g., dual bandpass filter). The method
further includes extinguishing the first light source, and then
illuminating the object a second time using the second light
source. The method including capturing a second set of images with
the plurality of photo-sensors during the second illumination. The
second set of images includes, for each respective photo-sensor in
the plurality of photo-sensors, an image corresponding to a second
spectral band transmitted by the corresponding multi-bandpass
filter (e.g., dual bandpass filter), where the light falling within
the second spectral range includes light falling within the second
spectral band of each multi-bandpass filter (e.g., dual bandpass
filter).
In some embodiments, each respective photo-sensor in the plurality
of photo-sensors is a pixel array that is controlled by a
corresponding shutter mechanism that determines an image
integration time for the respective photo-sensor. A first
photo-sensor in the plurality of photo-sensors is independently
associated with a first integration time for use during the first
image capture and a second integration time for use during the
second image capture. The first integration time is independent of
the second integration time. In other words, the device determines
separate integration times for each spectral band at which an image
is captured.
In some embodiments, each respective photo-sensor in the plurality
of photo-sensors is a pixel array that is controlled by a
corresponding shutter mechanism that determines an image
integration time for the respective photo-sensor. A duration of the
first illumination is determined by a first maximum integration
time associated with the plurality of photo-sensors during the
first image capture, where an integration time of a first
photo-sensor in the plurality of photo-sensors is different than an
integration time of a second photo-sensor in the plurality of
photo-sensors during the first image capture. A duration of the
second illumination is determined by a second maximum integration
time associated with the plurality of photo-sensors during the
second capture, where an integration time of the first photo-sensor
is different than an integration time of the second photo-sensor
during the second capture. In some implementations, the first
maximum integration time is different than the second maximum
integration time.
In some embodiments, each beam splitter in the plurality of beam
splitters exhibits a ratio of light transmission to light
reflection of about 50:50.
In some embodiments, at least one of the beam splitters in the
plurality of beam splitters is a dichroic beam splitter.
In some embodiments, at least the first beam splitter (e.g., in
direct optical communication with the lens) is a dichroic beam
splitter.
In some embodiments, at least one of the beam splitters in the
plurality of beam splitters is a dichroic beam splitter, the first
spectral range includes at least two discontinuous spectral
sub-ranges, each of the plurality of beam splitters exhibits a
ratio of light transmission to light reflection of about 50:50, and
the first beam splitter is configured to transmit light falling
within a third spectral range and reflect light falling within a
fourth spectral range.
In some embodiments, the plurality of beam splitters includes the
first beam splitter, the second beam splitter, and a third beam
splitter.
In some embodiments, the light falling within the third spectral
range is transmitted toward the second beam splitter, and the light
falling within the fourth spectral range is reflected toward the
third beam splitter.
In some embodiments, the second and the third beam splitters are
wavelength-independent beam splitters.
In some embodiments, the third spectral range includes light
falling within both the first and the second spectral ranges, and
the fourth spectral range includes light falling within both the
first and the second spectral ranges.
In some embodiments, the first beam splitter is a plate dichroic
beam splitter or a block dichroic beam splitter. In some
embodiments, the first beam splitter, the second beam splitter, and
the third beam splitter are dichroic beam splitters.
In some embodiments, the first spectral range includes at least two
discontinuous spectral sub-ranges, each of the plurality of beam
splitters exhibits a ratio of light transmission to light
reflection of about 50:50, the first beam splitter is configured to
transmit light falling within a third spectral range and reflect
light falling within a fourth spectral range, the plurality of beam
splitters includes the first beam splitter, the second beam
splitter, and a third beam splitter, and the first beam splitter,
the second beam splitter, and the third beam splitter are dichroic
beam splitters.
In some embodiments, the third spectral range includes at least two
discontinuous spectral sub-ranges, and the fourth spectral range
includes at least two discontinuous spectral sub-ranges.
In some embodiments, the light falling within the third spectral
range is transmitted toward the second beam splitter, and the light
falling within the fourth spectral range is reflected toward the
third beam splitter.
In some embodiments, the second beam splitter is configured to
reflect light falling within a fifth spectral range that includes
at least two discontinuous spectral sub-ranges and transmit light
not falling within either of the at least two discontinuous
spectral sub-ranges of the fifth spectral sub-range.
In some embodiments, the third beam splitter is configured to
reflect light falling within a sixth spectral range that includes
at least two discontinuous spectral sub-ranges and transmit light
not falling within either of the at least two discontinuous
spectral sub-ranges of the sixth spectral sub-range.
In some embodiments, the first beam splitter, the second beam
splitter, and the third beam splitter are each either a plate
dichroic beam splitter or a block dichroic beam splitter.
In some embodiments, the first light source is in a first lighting
assembly and the second light source is in a second lighting
assembly separate from the first lighting assembly.
In some embodiments, each image in the plurality of images is a
multi-pixel image of a location on the object, the method performed
by the controller also includes combining each image in the
plurality of images, on a pixel by pixel basis, to form a composite
image.
In some embodiments (e.g., where tri-bandpass filters or
quad-bandpass filters are employed), the imaging system includes
more than two light sources. In one embodiment, the imaging device
includes at least three light sources. In one embodiment, the
imaging includes at least four light sources. In one embodiment,
the imaging device includes at least five light sources.
In some embodiments, the imaging device is portable and powered
independent of a power grid during the first and second
illuminations. The first light source provides at least 80 watts of
illuminating power during the first illumination. The second light
source provides at least 80 watts of illuminating power during the
second illumination. The imaging device further includes a
capacitor bank in electrical communication with the first light
source and the second light source, wherein a capacitor in the
capacitor bank has a voltage rating of at least 2 volts and a
capacitance rating of at least 80 farads.
In some embodiments, the first and second wavelengths provide an
illuminating power, during their respective illuminations, selected
independently from between 20 watts and 400 watts. In some
embodiments, the illuminating powers are independently selected
from about 20 watts, 30 watts, 40 watts, 50 watts, 60 watts, 70
watts, 80 watts, 90 watts, 100 watts, 110 watts, 120 watts, 130
watts, 140 watts, 150 watts, 160 watts, 170 watts, 180 watts, 190
watts, 200 watts, 225 watts, 250 watts, 275 watts, 300 watts, 325
watts, 350 watts, 375 watts, and 400 watts.
In some embodiments, discrete bands of a multi-bandpass filter are
each separated by at least 60 nm. In a particular embodiment, the
two discrete bands of a dual bandpass filter in the plurality of
dual bandpass filters are separated by at least 60 nm.
In some embodiments, the imaging device is portable and
electrically independent of a power grid during the first and
second illuminations (or during all illuminations where more than
two illuminations are employed). In some embodiments, the first and
second illuminations occur for less than 300 milliseconds (or all
illuminations last for less than 300 milliseconds where more than
two illuminations are employed).
In some embodiments, the imaging device also includes a first
circuit board positioned on a first side of the optical path
assembly, where a first photo-sensor and a third photo-sensor in
the plurality of photo-sensors are coupled to the first circuit
board. A second circuit board positioned on a second side of the
optical path assembly opposite to the first side, where the second
circuit board is substantially parallel with the first circuit
board, where a second photo-sensor and a fourth photo-sensor in the
plurality of photo-sensors are coupled to the second circuit board.
The first beam splitter is configured to split light received from
the lens into a first optical path and a second optical path, where
the first optical path is substantially collinear with the optical
axis, and the second optical path is substantially perpendicular to
the optical axis. The second beam splitter is configured split
light from the first optical path into a third optical path and a
fourth optical path, where the third optical path is substantially
collinear with the first optical path, and the fourth optical path
is substantially perpendicular to the optical axis. A third beam
splitter in the plurality of beam splitters is configured to split
light from the second optical path into a fifth optical path and a
sixth optical path, where the fifth optical path is substantially
collinear with the second optical path, and the sixth optical path
is substantially perpendicular to the second optical path. The
optical path assembly also includes a first beam steering element
configured to deflect light from the third optical path
perpendicular to the third optical path and onto the first
photo-sensor coupled to the first circuit board, a second beam
steering element configured to deflect light from the fourth
optical path perpendicular to the fourth optical path and onto the
second photo-sensor coupled to the second circuit board, a third
beam steering element configured to deflect light from the fifth
optical path perpendicular to the fifth optical path and onto the
third photo-sensor coupled to the first circuit board, and a fourth
beam steering element configured to deflect light from the sixth
optical path perpendicular to the sixth optical path and onto the
fourth photo-sensor coupled to the second circuit board.
In some embodiments, a first multi-bandpass filter (e.g., dual
bandpass filter) is positioned in the third optical path between
the first beam splitter and the first photo-sensor. A second
multi-bandpass filter (e.g., dual bandpass filter) is positioned in
the fourth optical path between the second beam splitter and the
second photo-sensor. A third multi-bandpass filter (e.g., dual
bandpass filter) is positioned in the fifth optical path between
the third beam splitter and the third photo-sensor. A fourth
multi-bandpass filter (e.g., dual bandpass filter) is positioned in
the sixth optical path between the fourth beam splitter and the
fourth photo-sensor.
In some embodiments, the imaging device also includes a polarizing
filter disposed along the optical axis. In some embodiments, the
polarizing filter is adjacent to the lens and before the first beam
splitter along the optical axis.
In some embodiments, the first beam steering element is a mirror or
prism.
In some embodiments, the first beam steering element is a folding
prism.
In some embodiments, each respective beam splitter and each
respective beam steering element is oriented along substantially
the same plane.
In some embodiments, each respective photo-sensor is flexibly
coupled to its corresponding circuit board.
In some embodiments, the first beam splitter, the second beam
splitter, and the third beam splitter each exhibits a ratio of
light transmission to light reflection of about 50:50.
In some embodiments, at least the first beam splitter is a dichroic
beam splitter.
In some embodiments, the first beam splitter is configured to
transmit light falling within a first spectral range and reflect
light falling within a second spectral range.
In some embodiments, the light falling within the first spectral
range is transmitted toward the second beam splitter, and the light
falling within the second spectral range is reflected toward the
third beam splitter.
In some embodiments, the second and the third beam splitters are
wavelength-independent beam splitters.
In some embodiments, the first beam splitter, the second beam
splitter, and the third beam splitter are dichroic beam
splitters.
In some embodiments, the first beam splitter is configured to
transmit light falling within a first spectral range that includes
at least two discontinuous spectral sub-ranges and reflect light
falling within a second spectral range that includes at least two
discontinuous spectral sub-ranges.
In some embodiments, the second beam splitter is configured to
reflect light falling within a third spectral range that includes
at least two discontinuous spectral sub-ranges and transmit light
not falling within either of the at least two discontinuous
spectral sub-ranges of the third spectral sub-range.
In some embodiments, the third beam splitter is configured to
reflect light falling within a fourth spectral range that includes
at least two discontinuous spectral sub-ranges and transmit light
not falling within either of the at least two discontinuous
spectral sub-ranges of the fourth spectral sub-range.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the present disclosure can be understood in greater detail,
a more particular description may be had by reference to the
features of various implementations, some of which are illustrated
in the appended drawings. The appended drawings, however, merely
illustrate the more pertinent features of the present disclosure
and are therefore not to be considered limiting, for the
description may admit to other effective features and
arrangements.
FIG. 1A is an illustration of a hyperspectral imaging device 100,
in accordance with an implementation.
FIG. 1B is an illustration of a hyperspectral imaging device 100,
in accordance with an implementation.
FIG. 2A and FIG. 2B are illustrations of an optical assembly 102 of
a hyperspectral imaging device 100, in accordance with
implementations of the disclosure.
FIG. 3 is an exploded schematic view of an implementation of an
optical assembly 102 of a hyperspectral imaging device 100.
FIG. 4 is an exploded schematic view of the optical paths 400-404
of an implementation of an optical assembly 102 of a hyperspectral
imaging device 100.
FIG. 5A, FIG. 5B, and FIG. 5C are two-dimensional schematic
illustrations of the optical paths 500-506 and 600-606 of
implementations of an optical assembly 102 of a hyperspectral
imaging device 100.
FIG. 6 is an illustration of a front view of implementations of an
optical assembly 102 of a hyperspectral imaging device 100.
FIG. 7 is a partially cut-out illustration of a bottom view of a
hyperspectral imaging device 100, in accordance with an
implementation.
FIG. 8A is a partially cut-out illustration of a bottom view of a
hyperspectral imaging device 100 and optical paths, in accordance
with an implementation.
FIG. 8B is a partially cut-out illustration of a bottom view of a
hyperspectral imaging device 100 and optical paths, in accordance
with another implementation.
FIG. 9A, FIG. 9B and FIG. 9C are illustrations of framing guides
902 projected onto the surface of an object for focusing an image
collected by implementations of a hyperspectral imaging device
100.
FIGS. 9D and 9E are illustrations of point guides 903 projected
onto the surface of an object for focusing an image collected by
implementations of a hyperspectral imaging device 100.
FIG. 10 is a two-dimensional schematic illustration of the optical
paths of an implementation of an optical assembly 102 of a
hyperspectral imaging device 100.
FIG. 11 is a two-dimensional schematic illustration of the optical
paths of another implementation of an optical assembly 102 of a
hyperspectral imaging device 100.
FIG. 12 is a two-dimensional schematic illustration of the optical
paths of an implementation of an optical assembly 102 of a
hyperspectral imaging device 100.
FIG. 13 is an illustration of a first view of another hyperspectral
imaging device 100, in accordance with an implementation.
FIG. 14 is an illustration of a second view of the hyperspectral
imaging device 100 of FIG. 13, in accordance with an
implementation.
In accordance with common practice the various features illustrated
in the drawings may not be drawn to scale. Accordingly, the
dimensions of the various features may be arbitrarily expanded or
reduced for clarity. In addition, some of the drawings may not
depict all of the components of a given system, method or device.
Finally, like reference numerals may be used to denote like
features throughout the specification and figures.
DETAILED DESCRIPTION
Numerous details are described herein in order to provide a
thorough understanding of the example implementations illustrated
in the accompanying drawings. However, the invention may be
practiced without many of the specific details. And, well-known
methods, components, and circuits have not been described in
exhaustive detail so as not to unnecessarily obscure more pertinent
aspects of the implementations described herein.
Hyperspectral imaging typically relates to the acquisition of a
plurality of images, where each image represents a narrow spectral
band collected over a continuous spectral range. For example, a
hyperspectral imaging system may acquire 15 images, where each
image represents light within a different spectral band. Acquiring
these images typically entails taking a sequence of photographs of
the desired object, and subsequently processing the multiple images
to generate the desired hyperspectral image. In order for the
images to be useful, however, they must be substantially similar in
composition and orientation. For example, the subject of the images
must be positioned substantially identically in each frame in order
for the images to be combinable into a useful hyperspectral image.
Because images are captured sequentially (e.g., one after another),
it can be very difficult to ensure that all of the images are
properly aligned. This can be especially difficult in the medical
context, where a clinician is capturing images of a patient who may
move, or who may be positioned in a way that makes imaging the
subject area difficult or cumbersome.
As described herein, a hyperspectral imaging device is described
that concurrently captures multiple images, where each image is
captured in a desired spectral band. Specifically, the disclosed
imaging device and associated methods use multiple photo-sensors to
capture a plurality of images concurrently. Thus, a user does not
need to maintain perfect alignment between the imaging device and a
subject while attempting to capture multiple discrete images, and
can instead simply position the imaging device once and capture all
of the required images in a single operation (e.g., with, one, two,
or three exposures) of the imaging device. Accordingly,
hyperspectral images can be acquired faster and more simply, and
with more accurate results.
Conventional imaging systems also suffer from high power budget
demands, requiring the system to be plugged into a power source
(e.g., an alternating current outlet) for operation. This arises
from the use of tunable filter elements, high powered light
sources, etc. Advantageously, the optical architecture of the
hyperspectral imaging devices described herein reduces the power
burden and overall size of the system, allowing production of a
truly portable device.
In one implementation, the design of the hyperspectral imaging
devices described herein solve these problems by employing a
plurality of photo-sensors configured to concurrently acquire
images of an object (e.g., a tissue of a patient) at different
spectral bands. Each photo-sensor is configured to detect a limited
number of spectral bands (e.g., 1 or 2 spectral bands), but
collectively, the plurality of photo-sensors capture images at all
of the spectral bands required to construct a particular
hyperspectral data cube (e.g., a hyperspectral data cube useful for
generating a particular medical diagnosis, performing surveillance,
agricultural surveying, industrial evaluation, etc.).
In some implementations, these advantages are realized by
separating and directing light within an optical assembly in the
imaging device such that each photo-sensor is irradiated with light
of only limited spectral bands. An example of the optical paths
created within the optical assembly of such an implementation is
illustrated in FIG. 11, which splits light into component spectral
bands (e.g., using dichroic beam splitters and/or beam splitting
plates) and direct appropriate spectral bands of light to
corresponding photo-sensors.
In some implementations, these advantages are realized by evenly
distributing light towards each photo-sensor within an optical
assembly, and then filtering out unwanted wavelengths prior to
detection by each photo-sensor. An example of the optical paths
created within the optical assembly of such an implementation is
illustrated in FIG. 10, which uses optical elements (e.g., 50:50
beam splitters) to evenly distribute light towards filter elements
covering each respective photo-sensor.
In yet other implementations, these advantages are realized by
employing a hybrid of these two strategies. For example, with an
optical assembly that first separates light (e.g., with a dichroic
beam splitter or beam splitting plate) and then evenly distributes
component spectral bands to respective photo-sensors covered by
filters having desired passband spectrums.
In some implementations, one or more of these advantages are
realized by employing two illumination sources in the hyperspectral
imaging device. The first illumination source is configured to
illuminate an object with a first sub-set of spectral bands, and
the second illumination configured to illuminate the object with a
second sub-set of spectral bands. The first and second subsets of
spectral bands do not overlap, but together include all the
spectral bands required to construct a particular hyperspectral
data cube. The optical assembly is configured such that two sets of
images are collected, the first while the object is illuminated
with the first light source and the second while the object is
illuminated with the second light source. For example, each
photo-sensor captures a first image at a first spectral band
included in the first sub-set of spectral bands and a second image
at a second spectral band included in the second sub-set of
spectral bands.
In some implementations, image capture and processing includes the
imaging device collecting a plurality of images of a region of
interest on a subject (e.g., a first image captured at a first
spectral bandwidth and a second image captured at a second spectral
bandwidth). The imaging device stores each respective image at a
respective memory location (e.g., the first image is stored at a
first location in memory and the second image is stored at a second
location in memory). And the imaging device compares, on a
pixel-by-pixel basis, e.g., with a processor 210, each pixel of the
respective images to produce a hyperspectral image of the region of
interest of the subject. In some implementations, individual pixel
values are binned, averaged, or otherwise arithmetically
manipulated prior to pixel-by-pixel analysis, e.g., pixel-by-pixel
comparison includes comparison of binned, averaged, or otherwise
arithmetically manipulated pixel values.
Exemplary Implementations
FIG. 1A illustrates a hyperspectral imaging device 100, in
accordance with various implementations. The hyperspectral imaging
device 100 includes an optical assembly 102 having at least one
light source 106 for illuminating the surface of an object (e.g.,
the skin of a subject) and a lens assembly 104 for collecting light
reflected and/or back scattered from the object. The optical
assembly 102 is mounted onto a docking station 110.
In various implementations, optical assembly 102 is permanently
fixed onto the docking station 110 (e.g., optical assembly 102 is
held in place by a substructure of docking station 110 partially
encasing optical assembly 102 and fastened through welding, screws,
or other means). In other implementations, optical assembly 102 is
not permanently fixed onto the docking station 110 (e.g., optical
assembly 102 snaps into a substructure of docking station 110).
In various optional implementations, and with reference to FIG. 1A,
docking station 110 includes first and second projectors 112-1 and
112-2 configured to project light onto the object indicating when
the hyperspectral imaging device 100 is positioned at an
appropriate distance from the object to acquire a focused image.
This may be particularly useful where the lens assembly 104 has a
fixed focal distance, such that the image cannot be brought into
focus by manipulation of the lens assembly.
Referring additionally to FIGS. 8A and 9C, in various
implementations, first projector 112-1 and second projector 112-2
of FIG. 1A are configured to project patterns of light onto the
to-be-imaged object including a first portion 902-1 and a second
portion 902-2 that together form a shape 902 on the object when
properly positioned (see, e.g., FIGS. 8A and 9C). For example, the
first portion of the shape 902-1 and the second portion of the
shape 902-1 are configured to converge to form the shape 902 when
the lens 104 is positioned at a predetermined distance from the
object, the predetermined distance corresponding to a focal
distance of the lens assembly 104.
In various implementations, first projector 112-1 and second
projector 112-2 are each configured to project a spot onto the
object, such that the spots converge when the lens 104 is
positioned at a predetermined distance from the object
corresponding to a focus distance of the lens (see, e.g., FIGS. 8B
and 9E). Other projections are also contemplated, including other
shapes, reticles, images, crosshairs, etc.
In various implementations, docking station 110 includes an optical
window 114 configured to be positioned between light source 106 and
an object to be imaged. Window 114 is also configured to be
positioned between lens assembly 104 and the object to be imaged.
Optical window 114 protects light source 106 and lens assembly 104,
as well as limits ambient light from reaching lens assembly 104. In
various implementations, optical window 114 consists of a material
that is optically transparent (or essentially optically
transparent) to the wavelengths of light emitted by light source
106. In various implementations, optical window 114 consists of a
material that is partially or completely opaque to one or more
wavelengths of light not emitted by light source 106. In various
implementations, optical window 114 serves as a polarizing lens. In
various implementations, optical window 114 is open to the external
environment (e.g., does not include an installed lens or other
optically transparent material).
In various implementations, docking station 110 is configured to
receive a mobile device 120, such as a smart phone, a personal
digital assistant (PDA), an enterprise digital assistant, a tablet
computer, an IPOD, a digital camera, a portable music player,
and/or other portable electronic devices, effectively mounting the
mobile device onto hyperspectral imaging device 100. In various
implementations, docking station 110 is configured to facilitate
electronic communication between optical assembly 102 and mobile
device 120. In various implementations, mobile device 120 includes
display 122 configured to act as a display for optical assembly 102
(e.g., as a touch screen display for operating optical assembly 102
and/or as a display for hyperspectral images collected by optical
assembly 102). In various implementations, mobile device 120 is
configured as a processor for processing one or more images
collected by optical assembly 102. In various implementations,
mobile device 120 is configured to transmit one or more images
collected by optical assembly 102 to an external computing device
(e.g., by wired or wireless communication).
FIG. 1B illustrates another hyperspectral imaging device 100, in
accordance with various implementations, similar to that shown in
FIG. 1A but including an integrated body 101 that resembles a
digital single-lens reflex (DSLR) camera in that the body has a
forward-facing lens assembly 104, and a rearward facing display
122. The DSLR-type housing allows a user to easily hold
hyperspectral imaging device 100, aim it toward a patient and the
region of interest (e.g., the skin of the patient), and position
the device at an appropriate distance from the patient. One will
appreciate that the implementation of FIG. 1B, may incorporate the
various features described above and below in connection with the
device of FIG. 1A.
In various implementations, and similar to the device described
above, the hyperspectral imaging device 100 illustrated in FIG. 1B
includes an optical assembly having light sources 106 and 107 for
illuminating the surface of an object (e.g., the skin of a subject)
and a lens assembly 104 for collecting light reflected and/or back
scattered from the object.
In various implementations, and also similar to the device
described above, the hyperspectral imaging device of FIG. 1B
includes first and second projectors 112-1 and 112-2 configured to
project light onto the object indicating when the hyperspectral
imaging device 100 is positioned at an appropriate distance from
the object to acquire a focused image. As noted above, this may be
particularly useful where the lens assembly 104 has a fixed focus
distance, such that the image cannot be brought into focus by
manipulation of the lens assembly. As shown in FIG. 1B, the
projectors are mounted on a forward side of body 101.
In various implementations, the body 101 substantially encases and
supports the light sources 106 and 107 and the lens assembly 104 of
the optical assembly, along with the first and second projectors
112-1 and 112-2 and the display 122.
In contrast to the above-described device, various implementations
of the hyperspectral imaging device of FIG. 1B include
photo-sensors mounted on substantially vertically-oriented circuit
boards (see, e.g., photo sensors 210-1, 210-3). In various
implementations, the hyperspectral imaging device includes a
live-view camera 103 and a remote thermometer 105. The live-view
camera 103 enables the display 122 to be used as a viewfinder, in a
manner similar to the live preview function of DSLRs. The
thermometer 105 is configured to measure the temperature of the
patient's tissue surface within the region of interest.
FIG. 2A is a cutaway view of the optical assembly 102 for a
hyperspectral imaging device 100, in accordance with various
implementations. The optical assembly 102 may be incorporated into
a larger assembly (as discussed herein), or used independently of
any other device or assembly.
As shown in FIG. 2A, the optical assembly 102 includes a casing
202. As also shown in an exploded view in FIG. 3, the optical
assembly 102 also includes a lens assembly 104, at least one light
source (e.g., light source 106), an optical path assembly 204, one
or more circuit boards (e.g., circuit board 206 and circuit board
208), and a plurality of photo-sensors 210 (e.g., photo-sensors
210-1 . . . 210-4). One will appreciate that the imaging device 100
is provided with one or more processors and a memory. For example,
such processors may be integrated or operably coupled with the one
or more circuit boards. For instance, in some embodiments, an
AT32UC3A364 (ATMEL corporation, San Jose Calif.) microcontroller,
or equivalent, coupled to one or more floating point gate arrays,
is used to collect images from the photo-sensors. Although
illustrated with two circuit boards 206 and 208, in some
implementations, the hyperspectral imaging device has a single
circuit board (e.g., either 206 or 208) and each photo-sensor 210
is either mounted on the single circuit board or connected to the
circuit board (e.g., by a flex circuit or wire).
Components of the optical assembly 102 are housed in and/or mounted
to the casing 202. In various implementations, the casing 202 is
itself configured to be housed in and/or mounted to another
assembly, as shown in FIG. 1A.
The lens assembly 104 (also referred to interchangeably herein as a
"lens") is an imaging lens that is configured to capture light
reflected from objects, focus the light, and direct the light into
the optical path assembly 204. In various implementations, the lens
assembly 104 is a multi-element lens having a fixed focal length, a
fixed focus distance, and/or is a fixed-focus lens.
The at least one light source is configured to direct light onto an
object to be imaged by the optical assembly 102. Specifically, the
at least one light source is configured to illuminate an object
with light having desired spectral content. Light from the at least
one light source that is reflected or backscattered from the object
is then received by the lens assembly 104 and captured by the
plurality of photo-sensors in the optical assembly 102.
In various implementations, as discussed herein, the at least one
light source is configured to operate according to two or more
modes of operation, where each mode of operation results in the
illumination of the object with light having different spectral
content. For example, in a first mode of operation, the at least
one light source emits light within a spectral range of 500 nm to
600 nm (or any other appropriate spectral range), and, in a second
mode of operation, the at least one light source emits light within
a spectral range of 600 nm to 700 nm (or any other appropriate
spectral range).
In various implementations, the light source includes a single
broadband light source, a plurality of broadband light sources, a
single narrowband light source, a plurality of narrowband light
sources, or a combination of one or more broadband light source and
one or more narrowband light source. Likewise, in various
embodiments, the light source includes a plurality of coherent
light sources, a single incoherent light source, a plurality of
incoherent light sources, or a combination of one or more coherent
and one or more incoherent light sources.
In one implementation, where a light source is configured to emit
light within two or more spectral ranges, the light source includes
two or more sets (e.g., each respective set including one or more
light sources configured to emit light of the same spectral band)
of light emitting devices (e.g., light emitting diodes), where each
respective set is configured to only emit light within one of the
two or more spectral ranges.
In some embodiments, referring to FIG. 1B, where a light source is
configured to emit light within two or more spectral ranges, the
light source includes two or more sets of light emitting devices
(e.g., light emitting diodes), where each respective set is
filtered by a respective filter (e.g., a bandpass filter). As a
specific example, referring to FIG. 1B, light source 106 is
configured to emit light within a first spectral range and light
source 107 is configured to emit light within a second spectral
range. In some embodiments, light source 106 comprises a first set
of light emitting devices that are filtered with a first bandpass
filter corresponding to the first spectral range, and light source
107 comprises a second set of light emitting devices filtered with
a second bandpass filters corresponding to the second spectral. In
typical embodiments the first spectral range is different from, and
non-overlapping, the first second spectral range. In some
embodiments the first spectral range is different from, but
overlapping, the second spectral range. In some embodiments the
first spectral range is the same as the second spectral range. In
some embodiments, the first set of light emitting devices consists
of a first single light emitting diode (LED) and the second set of
light emitting devices consists of a second single light emitting
diode. An example of a suitable light emitting diode for use as the
first single light emitting diode and the second single light
emitting diode in such embodiments is a LUMINUS CBT-140 White LED
(Luminus Devices, Inc., Billerica, Mass.). In some embodiments, the
first set of light emitting devices consists of a first plurality
of light emitting diode and the second set of light emitting
devices consists of a second plurality of light emitting
diodes.
In some embodiments the light source 106 is not covered by a
bandpass filter and natively emits only the first spectral range.
In some embodiments the second source 107 is not covered by a
bandpass filter and natively emits only the second spectral
range.
In some embodiments, the light source 106 emits at least 80 watts
of illuminating power and the second light source emits at least 80
watts of illuminating power. In some embodiments, the light source
independently 106 emits at least 80 watts, at least 85 watts, at
least 90 watts, at least 95 watts, at least 100 watts, at least 105
watts, or at least 110 watts of illuminating power. In some
embodiments, the light source 107 independently emits at least 80
watts, at least 85 watts, at least 90 watts, at least 95 watts, at
least 100 watts, at least 105 watts, or at least 110 watts of
illuminating power.
In some embodiments, the spectral imager 100 is not connected to a
main power supply (e.g., an electrical power grid) during
illumination. In other words, in some embodiments, the spectral
imager is independently powered, e.g. by a battery, during at least
the illumination stages. In some embodiments, in order to achieve
the amount of illuminating power needed by light source 106 and/or
light source 107 (e.g., more than 100 watts of illuminating power
in some embodiments), the light sources are in electrical
communication to the battery through a high performance capacity
bank (not shown). In one such example, the capacitor bank comprises
a board mountable capacitor. In one such example, the capacitor
bank comprises a capacitor having a rating of at least 80 farads
(F), a peak current of at least 80 amperes (A), and is capable of
delivering at least 0.7 watt-hours (Whr) of energy during
illumination. In one such example, the capacitor bank comprises a
capacitor having a rating of at least 90 F, a peak current of at
least 85 A, and is capable of delivering at least 0.8 Whr of energy
during illumination. In one such example, the capacitor bank
comprises a capacitor having a rating of at least 95 F, a peak
current of at least 90 A, and is capable of delivering at least 0.9
Whr of energy during illumination. In one such example, the
capacitor bank comprises an RSC2R7107SR capacitor (IOXUS, Oneonta,
N.Y.), which has a rating of 100 F, a peak current of 95 A, and is
capable of delivering 0.1 Whr of energy during illumination.
In one example, the battery used to power the spectral imager,
including the capacitor bank, has a voltage of at least 6 volts and
a capacity of at least 5000 mAH. In one such example, the battery
is manufactured by TENERGY (Fremont, Calif.), is rated for 7.4 V,
has a capacitance of 6600 mAH, and weighs 10.72 ounces.
In some embodiments, the capacitor bank comprises a single
capacitor in electrical communication with both the light source
106 and the light source 107, where the single capacitor has a
rating of at least 80 F, a peak current of at least 80 A, and is
capable of delivering at least 0.7 Whr of energy during
illumination. In some embodiments, the capacitor bank comprises a
first capacitor in electrical communication with the light source
106 and a second capacitor in electrical communication with light
source 107, where the first capacitor and the second capacitor each
have a rating of at least 80 F, a peak current of at least 80 A,
and are each capable of delivering at least 0.7 Whr of energy
during illumination.
In one implementation, where a light source is configured to emit
light within two or more spectral ranges, in a first mode of
operation, only the first set of light emitting devices are used,
and in a second mode of operation, only the second set of light
emitting devices are used. Here, it will be understood that the
first set of light emitting devices is a single first LED and the
second set of light emitting devices is a single second LED in some
embodiments. The same or a similar arrangement of light emitting
devices and bandpass filters may be used in other light sources of
the imaging device 100. Of course, additional modes of operations
(e.g., a third mode of operation, a fourth mode of operation, etc.)
are also possible by including additional sets of light emitting
devices and/or additional bandpass filters corresponding to
additional spectral ranges.
In various implementations, as shown in FIG. 2B, the optical
assembly 102 has two light sources, including light source 106 and
light source 107. In various implementations, both light sources
are configured to emit light falling within two substantially
non-overlapping spectral ranges. For example, in a first mode of
operation, both light sources 106 and 107 emit light within a
spectral range of 500 nm to 600 nm (or any other appropriate
spectral range), and in a second mode of operation both light
sources 106 and 107 emit light within a spectral range of 600 nm to
700 nm (or any other appropriate spectral range).
In some implementations where the hyperspectral imaging device
includes two light sources (e.g., light sources 106 and 107), each
light source is configured to emit light falling within only one of
the two substantially non-overlapping spectral ranges. For example,
in a first mode of operation, light source 106 emits light within a
first spectral range (e.g., 500 nm to 600 nm, or any other
appropriate spectral range), and in a second mode of operation,
light source 107 emits light within a second spectral range (e.g.,
600 nm to 700 nm, or any other appropriate spectral range).
In some implementations where the hyperspectral imaging device
includes two light sources (e.g., light sources 106 and 107), each
light source is configured to emit light falling within a
corresponding predetermined spectral range. For example, in a first
mode of operation, light source 106 emits light within a first
spectral range (e.g., one that encompasses 520 nm, 540 nm, 560 nm
and 640 nm light), and in a second mode of operation, light source
107 emits light within a second spectral range (e.g. one that
encompasses 580 nm, 590 nm, 610 nm and 620 nm light).
In some embodiments the first and second modes of light operation
apply to the pair of light sources. In other words, while each
respective light source only emits light falling within one
respective spectral range, the pair of light sources together
operate according to the first and the second modes of operation
described above.
In various implementations, one or both of the two substantially
non-overlapping spectral ranges are non-contiguous spectral ranges.
For example, a first light source may emit light having wavelengths
between 490 nm and 580 nm in a discontinuous fashion (e.g., in
spectral bands of 490-510 nm and 520-580 nm), and a second light
source may emit light having wavelengths between 575 nm and 640 in
a continuous fashion (e.g., in a single spectral band of 575-640
nm). In another example, a first light source may emit light having
wavelengths between 510 nm and 650 nm in a discontinuous fashion
(e.g., in spectral bands of 510-570 nm and 630-650 nm), and a
second light source may emit light having wavelengths between 570
nm and 630 in a continuous fashion (e.g., in a single spectral band
of 570-630 nm). In still another example, a light source 106 may
emit light having wavelengths between 515 nm and 645 nm in a
discontinuous fashion (e.g., in spectral bands of 515-565 nm and
635-645 nm), and light source 107 may emit light having wavelengths
between 575 nm and 625 in a continuous fashion (e.g., in a single
spectral band of 575-625 nm).
In some implementations, light sources 106 and 107 are broadband
light sources (e.g., white LEDs) covered by corresponding first and
second wavelength filters, having substantially overlapping pass
bands. In some implementations, light sources 106 and 107 are
broadband light sources (e.g., white LEDs) covered by corresponding
first and second wavelength filters, having substantially
non-overlapping pass bands. The pass bands of filters used in such
implementations are based on the identity of the spectral bands to
be imaged for creation of the hyperspectral data cube.
In one implementation, the spectral bands to be collected are
separated into two groups. The first group consisting of spectral
bands with wavelengths below a predetermined wavelength and the
second group consisting of spectral bands with wavelengths above a
predetermined wavelength. For example, if images at eight spectral
bands are needed to create a particular hyperspectral data cube,
the four spectral bands having the shortest wavelengths make up the
first group and the other four spectral bands make up the second
group. The first pass band is then selected such that the first
filter allows light having wavelengths corresponding to the first
group, but blocks substantially all light having wavelengths
corresponding to the second group. Likewise the second pass band is
selected such that the second filter allows light having
wavelengths corresponding to the second group, but blocks
substantially all light having wavelengths corresponding to the
first group.
In another implementation, the spectral bands to be collected are
separated into two groups. The first group consists of a first
subset of spectral bands and the second group consists of a second
subset of spectral bands. In this implementation, the division into
the two subsets is made in such a manner that, upon pairing a
spectral band from the first subset with a spectral band from the
second subset, a minimum predetermined band separation is
guaranteed. For instance, in one embodiment the first subset
comprises 520, 540, 560, and 640 whereas the second subset
comprises 580, 590, 510 and 620. Moreover, four pairs of
wavelengths are formed, each pair comprising one band from the
first subset and one band from the second subset, where the minimum
separation between the paired bands is at least 50 nm. For example,
in one embodiment the following pairs are formed: pair (i) 520
nm/590 nm, pair (ii) 540 nm/610 nm, pair (iii) 560 nm/620 nm, and
pair (iv) 580 nm/640 nm. Advantageously, paired bands where the
center of each band in the pair is at least 50 nm apart allows
facilitates the effectiveness of the dual bandpass filters used to
cover the photo-sensors in some embodiments, because the two
wavelengths ranges that each such bandpass filter permits to pass
through are far enough apart from each other to ensure filter
effectiveness. Accordingly, in some implementations, dual pass band
filters, allowing passage of one spectral band from the first group
and one spectral band from the second group, are placed in front of
each photo-sensor, such that one image is captured at a spectral
band belonging to the first group (e.g., upon illumination of the
object by light source 106), and one image is captured at a
spectral band belonging to the second group (e.g., upon
illumination of the object by light source 107).
In one implementation, where the hyperspectral data cube is used
for determining the oxyhemoglobin and deoxyhemoglobin content of a
tissue, the first filter has a pass band starting at between 430
and 510 nm and ending between 570 nm and 590 nm, and the second
filter has a pass band starting at between 570 nm and 580 nm and
ending between 645 nm and 700 nm.
In a first implementation, the imaging device 100 is configured to
collect a set of images, where each image in the set of images is
collected at a discrete spectral band, and the set of images
comprises images collected at any 4 or more, any 5 or more, any six
or more, any seven or more, or all of the set of discrete spectral
bands having central wavelengths {510.+-.5 nm, 530.+-.5 nm,
540.+-.5 nm, 560.+-.5 nm, 580.+-.5 nm, 590.+-.5 nm, 620.+-.5 nm,
and 660.+-.5 nm}, where each respective spectral band in the set
has a full width at half maximum of less than 15 nm, less than 10
nm, or 5 nm or less. In some embodiments of this first
implementation, a first bandpass filter, covering light source 106,
has a first pass band that permits wavelengths 500.+-.5-550.+-.5 nm
and a second pass band that permits wavelengths 650.+-.5-670.+-.5
nm while all other wavelengths are blocked, and a second bandpass
filter, covering light source 107, has a single pass band that
permits wavelengths 550.+-.5 nm-630.+-.5 nm while all other
wavelengths are blocked. In other such embodiments of this first
implementation, a first bandpass filter, covering light source 106,
has a first pass band that permits wavelengths 505.+-.5-545.+-.5 nm
and a second pass band that permits wavelengths 655.+-.5-665.+-.5
nm while all other wavelengths are blocked, and a second bandpass
filter, covering light source 107, has a single pass band that
permits wavelengths 555.+-.5 nm-625.+-.5 nm while all other
wavelengths are blocked.
In a second implementation, the imaging device 100 is configured to
collect a set of images, where each image in the set of images is
collected at a discrete spectral band, and the set of images
comprises images collected at any four or more, any five or more,
any six or more, any seven or more, or all of the set of discrete
spectral bands having central wavelengths {520.+-.5 nm, 540.+-.5
nm, 560.+-.5 nm, 580.+-.5 nm, 590.+-.5 nm, 610.+-.5 nm, 620.+-.5
nm, and 640.+-.5 nm} where each respective spectral band in the set
has a full width at half maximum of less than 15 nm, less than 10
nm, or 5 nm or less. In some embodiments of this second
implementation, a first bandpass filter, covering light source 106,
has a first pass band that permits wavelengths 510.+-.5-570.+-.5 nm
and a second pass band that permits wavelengths 630.+-.5-650.+-.5
nm while all other wavelengths are blocked, and a second bandpass
filter, covering light source 107, has a single pass band that
permits wavelengths 570.+-.5 nm-630.+-.5 nm, while all other
wavelengths are blocked. In other such embodiments of this second
implementation, a first bandpass filter, covering light source 106,
has a first pass band that permits wavelengths 515.+-.5-565.+-.5 nm
and a second pass band that permits wavelengths 635.+-.5-645.+-.5
nm while all other wavelengths are blocked, and a second bandpass
filter, covering light source 107, has a single pass band that
permits wavelengths 575.+-.5 nm-625.+-.5 nm while all other
wavelengths are blocked.
In a third implementation, the imaging device 100 is configured to
collect a set of images, where each image in the set of images is
collected at a discrete spectral band, and the set of images
comprises images collected at any four or more, any five or more,
any six or more, any seven or more, or all of the set of discrete
spectral bands having central wavelengths {500.+-.5 nm, 530.+-.5
nm, 545.+-.5 nm, 570.+-.5 nm, 585.+-.5 nm, 600.+-.5 nm, 615.+-.5
nm, and 640.+-.5 nm} where each respective spectral band in the set
has a full width at half maximum of less than 15 nm, less than 10
nm, or 5 nm or less. In some embodiments of this third
implementation, a first bandpass filter, covering light source 106,
has a first pass band that permits wavelengths 490.+-.5-555.+-.5 nm
and a second pass band that permits wavelengths 630.+-.5-650.+-.5
nm while all other wavelengths are blocked, and a second bandpass
filter, covering light source 107, has a single pass band that
permits wavelengths 560.+-.5 nm-625.+-.5 nm, while all other
wavelengths are blocked. In other such embodiments of this third
implementation, a first bandpass filter, covering light source 106,
has a first pass band that permits wavelengths 495.+-.5-550.+-.5 nm
and a second pass band that permits wavelengths 635.+-.5-645.+-.5
nm while all other wavelengths are blocked, and a second bandpass
filter, covering light source 107, has a single pass band that
permits wavelengths 565.+-.5 nm-620.+-.5 nm while all other
wavelengths are blocked.
In some implementations, light sources 106 and 107 are broadband
light sources (e.g., white LEDs). First light source 106 is covered
by a short pass filter (e.g., a filter allowing light having
wavelengths below a cut-off wavelength to pass through while
blocking light having wavelengths above the cut-off wavelength) and
second light source 107 is covered by a long pass filter (e.g., a
filter allowing light having wavelengths above a cut-on wavelength
to pass through while blocking light having wavelengths below the
cut-on wavelength). The cut-off and cut-on wavelengths of the short
and long pass filters are determined based on the set of spectral
bands to be captured by the imaging system. Generally, respective
cut-off and cut-on wavelengths are selected such that they are
longer than the longest wavelength to be captured in a first set of
images and shorter than the shortest wavelength to be captured in a
second set of images (e.g., where the first and second set of
images are combined to form a hyperspectral data set).
For example, referring to FIG. 2B and FIG. 3, in one
implementation, photo-sensors 210 are each covered by a dual pass
band filter 216. Each dual pass band filter 216 allows light of
first and second spectral bands to pass through to the respective
photo-sensor 210. Cut-off and cut-on wavelengths for filters
covering light sources 106 and 107 are selected such that exactly
one pass band from each filter 216 is below the cut-off wavelength
of the filter covering light source 106 and the other pass band
from each filter 216 is above the cut-on wavelength of the filter
covering light source 107.
In one implementation, where the hyperspectral data cube is used
for determining the oxyhemoglobin and deoxyhemoglobin content of a
tissue, the cut-off wavelength of the short-pass filter covering
light source 106 and the cut-on wavelength of the long-pass filter
covering light source 107 are between 565 nm and 585 nm.
In a first implementation, the hyperspectral imaging device is
configured to collect images at spectral bands having central
wavelengths of 510.+-.5 nm, 530.+-.5 nm, 540.+-.5 nm, 560.+-.5 nm,
580.+-.5 nm, 590.+-.5 nm, 620.+-.5 nm, and 660.+-.5 nm, where each
respective spectral band has a full width at half maximum of less
than 15 nm, and the cut-off wavelength of a short-pass filter
covering light source 106 and cut-on wavelength of a long-pass
filter covering light source 107 are each independently 570.+-.5
nm.
In a second implementation, the hyperspectral imaging device is
configured to collect images at spectral bands having central
wavelengths of 520.+-.5 nm, 540.+-.5 nm, 560.+-.5 nm, 580.+-.5 nm,
590.+-.5 nm, 610.+-.5 nm, 620.+-.5 nm, and 640.+-.5 nm, where each
respective spectral band has a full width at half maximum of less
than 15 nm, and the cut-off wavelength of a short-pass filter
covering light source 106 and cut-on wavelength of a long-pass
filter covering light source 107 are each independently 585.+-.5
nm.
In a third implementation, the hyperspectral imaging device is
configured to collect images at spectral bands having central
wavelengths of 500.+-.5 nm, 530.+-.5 nm, 545.+-.5 nm, 570.+-.5 nm,
585.+-.5 nm, 600.+-.5 nm, 615.+-.5 nm, and 640.+-.5, where each
respective spectral band has a full width at half maximum of less
than 15 nm, and the cut-off wavelength of a short-pass filter
covering light source 106 and cut-on wavelength of a long-pass
filter covering light source 107 are each independently 577.5.+-.5
nm.
In various implementations, the imaging device 100 includes three
or more light sources (e.g., 2, 3, 4, 5, 6, or more light sources).
In such cases, any appropriate assignments of spectral ranges (or
any other desired characteristic) among the three or more light
sources may be used. For example, each light source can be
configured to emit light according to each mode of operation
desired. Thus, for example, if four substantially non-overlapping
spectral ranges are required from four light sources, each light
source may be configured to emit light within each of the four
spectral ranges. In other cases, each respective light source may
be configured to emit light within a different respective one of
the four spectral ranges. In yet other cases, two of the light
sources may be configured to emit light within each of two of the
four spectral ranges, and the other two light sources may be
configured to emit light within each of the remaining two spectral
ranges. Other assignments of spectral ranges among the light
sources are also contemplated.
With reference to FIG. 4, the optical assembly 102 also includes an
optical path assembly 204 that directs light received by the lens
assembly 104 to a plurality of photo-sensors 210 (e.g., 210-1, . .
. 210-4) coupled to the first and the second circuit boards 206,
208. In particular, as described herein, the optical path assembly
204 includes a plurality of beam splitters 212 (e.g., 212-1 . . .
212-3) and a plurality of beam steering elements 214 (e.g., 214-2,
214-4). The beam splitters 212 and the beam steering elements 214
are configured to split the light received by the lens assembly 104
into a plurality of optical paths, and direct those optical paths
onto the plurality of photo-sensors 210 of the optical assembly
102.
Beam splitters of several different types may be used in the
optical assembly 102 in various implementations. One type of beam
splitter that is used in various implementations is configured to
divide a beam of light into two separate paths that each have
substantially the same spectral content. For example, approximately
50% of the light incident on the beam splitter is transmitted in a
first direction, while the remaining approximately 50% is
transmitted in a second direction (e.g., perpendicular to the first
direction). Other ratios of the light transmitted in the two
directions may also be used in various implementations. For ease of
reference, this type of beam splitter is referred to herein as a
50:50 beam splitter, and is distinguished from a dichroic beam
splitter that divides a beam of light into to two separate paths
that each have a different spectral content. For example, a
dichroic beam splitter that receives light having a spectral range
of 450-650 nm (or more) may transmit light having a spectral range
of 450-550 nm in a first direction, and transmit light having a
spectral range of 550-650 nm in a second direction (e.g.,
perpendicular to the first direction).
In addition, other ranges may be utilized, including but not
limited to discontinuous spectral sub-ranges. For example, a first
spectral range includes a first spectral sub-range of about 450-550
nm and a second spectral sub-range of about 615-650 nm, and second,
third and fourth spectral ranges may be about 550-615 nm, 585-650
nm and 450-585 nm, respectively. Alternatively, various beam
splitters may be utilized to split light into a first spectral
range having a first spectral sub-range of about 450-530 nm and a
second spectral sub-range of about 600-650 nm, a second spectral
range of about 530-600 nm, a third spectral range having at least
two discontinuous spectral sub-ranges including a third spectral
sub-range of about 570-600 nm and a fourth spectral sub-range of
about 615-650 nm, a fourth spectral range having at least two
discontinuous spectral sub-ranges including a fifth spectral
sub-range of about 450-570 nm and a sixth spectral sub-range of
about 600-615 nm, at least two discontinuous spectral sub-ranges of
a fifth spectral range including a seventh spectral sub-range of
about 585-595 nm and an eighth spectral sub-range of about 615-625
nm, and at least two discontinuous spectral sub-ranges of a sixth
spectral range including a ninth spectral sub-range of about
515-525 nm and a tenth spectral sub-range of about 555-565 nm.
In various implementations, the beam splitters 212 are 50:50 beam
splitters. In various implementations, the beam splitters 212 are
dichroic beam splitters (e.g., beam splitters that divide a beam of
light into separate paths that each have a different spectral
content). In various implementations, the beam splitters 212
include a combination of 50:50 beam splitters and dichroic beam
splitters. Several specific examples of optical assemblies 102
employing beam splitters of various types are discussed herein.
The optical path assembly 204 is configured such that the image
that is provided to each of the photo-sensors (or, more
particularly, the filters that cover the photo-sensors) is
substantially identical (e.g., the same image is provided to each
photo-sensor). Because the photo-sensors 210 can all be operated
simultaneously, the optical assembly 102 is able to capture a
plurality of images of the same object at substantially the same
time (thus capturing multiple images that correspond to the same
lighting conditions of the object). Moreover, because each
photo-sensor 210-n is covered by a bandpass filter 216-n having a
different passband, each photo-sensor 210-n captures a different
spectral component of the image. These multiple images, each
representing a different spectral component, are then assembled
into a hyperspectral data cube for analysis.
In some embodiments, each photo-sensor 210-n is a pixel array. In
some embodiments each photo-sensor 210-n comprises 500,000 pixels,
1,000,000 pixels, 1,100,000 pixels, 1,200,000 pixels or more than
1,300,000 pixels. In an exemplary embodiment a photo-sensor in the
plurality of photo-sensors is a 1/2-inch megapixel CMOS digital
image sensor such as the MT9M001C12STM monochrome sensor (Aptina
Imaging Corporation, San Jose, Calif.).
FIG. 3 is an exploded schematic view of the optical assembly 102,
in accordance with various implementations. FIG. 3 further
illustrates the arrangement of the various components of the
optical assembly. In particular, the optical assembly 102 includes
a first circuit board 206 and a second circuit board 208, where the
first and second circuit boards 206, 208 are substantially parallel
to one another and are positioned on opposing sides of the optical
path assembly 204. In various implementations, the circuit boards
206, 208 are rigid circuit boards.
Coupled to the first circuit board 206 are a first photo-sensor
210-1 and a third photo-sensor 210-3. Coupled to the second circuit
board 208 are a second photo-sensor 210-2 and a fourth photo-sensor
210-4. In various implementations, the photo-sensors 210 are
coupled directly to their respective circuit boards (e.g., they are
rigidly mounted to the circuit board). In various implementations,
in order to facilitate precise alignment of the photo-sensors 210
with respect to the optical path assembly 204, the photo-sensors
210 are flexibly coupled to their respective circuit board. For
example, in some cases, the photo-sensors 210 are mounted on a
flexible circuit (e.g., including a flexible substrate composed of
polyamide, PEEK, polyester, or any other appropriate material). The
flexible circuit is then electronically coupled to the circuit
board 206, 208. In various implementations, the photo-sensors 210
are mounted to rigid substrates that are, in turn, coupled to one
of the circuit boards 206, 208 via a flexible interconnect (e.g., a
flexible board, flexible wire array, flexible PCB, flexible flat
cable, ribbon cable, etc.).
As noted above, the optical assembly 102 includes a plurality of
bandpass filters 216 (e.g., 216-1 . . . 216-4). The bandpass
filters 216 are positioned between the photo-sensors 210 and their
respective optical outlets of the optical path assembly 204. Thus,
the bandpass filters 216 are configured to filter the light that is
ultimately incident on the photo-sensors 210. In some embodiments,
each bandpass filter 216 is a dual bandpass filter.
In various implementations, each bandpass filter 216 is configured
to have a different pass band. Accordingly, even though the optical
path assembly 204 provides the same image to each photo-sensor (or,
more particularly, to the filters that cover the photo-sensors),
each photo-sensor actually captures a different spectral component
of the image. For example, as discussed in greater detail herein, a
first bandpass filter 216-1 may have a passband centered around 520
nm, and a second bandpass filter 216-2 may have a passband centered
around 540 nm. Thus, when the imaging device 100 captures an
exposure, the first photo-sensor 210-1 (which is filtered by the
first bandpass filter 216-1) will capture an image representing the
portion of the incoming light having a wavelength centered around
520 nm, and the second photo-sensor 210-2 (which is filtered by the
second bandpass filter 216-2) will capture an image representing
the portion of the incoming light having a wavelength around 540
nm. (As used herein, the term exposure refers to a single imaging
operation that results in the simultaneous or substantially
simultaneous capture of multiple images on multiple photo-sensors.)
These images, along with the other images captured by the third and
fourth photo sensors 210-3, 210-4 (each capturing a different
spectral band), are then assembled into a hyperspectral data cube
for further analysis.
In various implementations, at least a subset of the bandpass
filters 216 are configured to allow light corresponding to two (or
more) discrete spectral bands to pass through the filter. While
such filters may be referred to herein as dual bandpass filters,
this term is meant to encompass bandpass filters that have two
discrete passbands as well as those that have more than two
discrete passbands (e.g., triple-band bandpass filters,
quadruple-band bandpass filters, etc.). By using bandpass filters
that have multiple passbands, each photo-sensor can be used to
capture images representing several different spectral bands. For
example, the hyperspectral imaging device 100 will first illuminate
an object with light within a spectral range that corresponds to
only one of the passbands of each of the bandpass filters, and
capture an exposure under the first lighting conditions.
Subsequently, the hyperspectral imaging device 100 will illuminate
an object with light within a spectral range that corresponds to a
different one of the passbands on each of the bandpass filters, and
then capture an exposure under the second lighting conditions.
Thus, because the first illumination conditions do not include any
spectral content that would be transmitted by the second passband,
the first exposure results in each photo-sensor capturing only a
single spectral component of the image. Conversely, because the
second illumination conditions do not include any spectral content
that would be transmitted by the first passband, the second
exposure results in each photo-sensor capturing only a single
spectral component of the image.
As a more specific example, in various implementations, the
bandpass filters 216-1 through 216-4 each include one passband
falling within the range of 500-585 nm, and a second passband
falling within the range of 585-650 nm, as shown below in table
(1):
TABLE-US-00001 TABLE 1 Exemplary Central Eavelengths of Pass-bands
for Filters 216-1-216-4 Filter 216-1 Filter 216-2 Filter 216-3
Filter 216-4 Passband 1 520 nm 540 nm 560 nm 580 nm Passband 2 590
nm 610 nm 620 nm 640 nm
In one implementation, the light source 106 has two modes of
operation: in a first mode of operation, the light source 106 emits
light having wavelengths according to a first set of spectral bands
(e.g., below 585 nm, such as between 500 nm and 585 nm); in a
second mode of operation, the light source 106 emits light having
wavelengths according to a second set of spectral bands (e.g.,
above 585 nm, such as between 585 nm and 650 nm). Thus, when the
first exposure is captured using the first illumination mode, four
images are captured, where each image corresponds to a single
spectral component of the incoming light. Specifically, the image
captured by the first sensor 210-1 will include substantially only
that portion of the incoming light falling within a first passband
(e.g., centered around 520 nm), the image captured by the second
sensor 210-2 will include substantially only that portion of the
incoming light falling within a second passband (e.g., centered
around 540 nm), and so on. When the second exposure is captured
using the second illumination mode, four additional images are
captured, where each image corresponds to a single spectral
component of the incoming light. Specifically, the image captured
by the first sensor 210-1 will include substantially only that
portion of the incoming light falling within the other pass band
allowed by the dual band filter 216-1 (e.g., centered around 590
nm), the image captured by the second sensor 210-2 will include
substantially only that portion of the incoming light falling
within the other pass band allowed by dual band filter 216-2 (e.g.,
centered around 610 nm), and so on. The eight images resulting from
the two exposures described above are then assembled into a
hyperspectral data cube for further analysis.
In another implementation, as illustrated in FIG. 2B, the
hyperspectral imaging device has two light sources 106, 107, and
each light source is configured to illuminate an object with a
different set of spectral bands. The hyperspectral imaging device
has two modes of operation: in a first mode of operation, light
source 106 emits light having wavelengths according to a first set
of spectral bands. In a second mode of operation, light source 107
emits light having wavelengths according to a second set of
spectral bands. Thus, when the first exposure is captured using the
first illumination mode, four images are captured, where each image
corresponds to a single spectral component of the incoming light.
Specifically, the image captured by the first sensor 210-1 during
the first mode of operation will include substantially only that
portion of the incoming light falling within a first passband
(e.g., centered around 520 nm), the image captured by the second
sensor 210-2 during the first mode of operation will include
substantially only that portion of the incoming light falling
within a second passband (e.g., centered around 540 nm), and so on.
When the second exposure is captured using the second illumination
mode, four additional images are captured, where each image
corresponds to a single spectral component of the incoming light.
Specifically, the image captured by the first sensor 210-1 will
include substantially only that portion of the incoming light
falling within the other pass band allowed by the dual band filter
216-1 (e.g., centered around 590 nm), the image captured by the
second sensor 210-2 will include substantially only that portion of
the incoming light falling within the other pass band allowed by
dual band filter 216-2 (e.g., centered around 610 nm), and so on.
The eight images resulting from the two exposures described above
are then assembled into a hyperspectral data cube for further
analysis. In typical embodiments, each such image is a multi-pixel
image. In some embodiments, this assembly involves combining each
image in the plurality of images, on a pixel by pixel basis, to
form a composite image.
In the above examples, each filter 216-n has two passbands.
However, in various implementations, the filters do not all have
the same number of passbands. For example, if fewer spectral bands
need to be captured, one or more of the filters 216-n may have only
one passband. Similarly, one or more of the filters 216-n may have
additional passbands. In the latter case, the light source 104 will
have additional modes of operation, where each mode of operation
illuminates an object with light that falls within only 1 (or none)
of the passbands of each sensor.
FIG. 4 is an exploded schematic view of a portion of the optical
assembly 102, in accordance with various implementations, in which
the optical paths formed by the optical path assembly 204 are
shown. The optical path assembly 204 channels light received by the
lens assembly 104 to the various photo-sensors 210 of the optical
assembly 102.
Turning to FIG. 4, the optical assembly 102 includes a first beam
splitter 212-1, a second beam splitter 212-2, and a third beam
splitter 212-3. Each beam splitter is configured to split the light
received by the beam splitter into at least two optical paths. For
example, beam splitters for use in the optical path assembly 204
may split an incoming beam into one output beam that is collinear
to the input beam, and another output beam that is perpendicular to
the input beam.
Specifically, the first beam splitter 212-1 is in direct optical
communication with the lens assembly 104, and as shown in FIG. 10,
splits the incoming light (represented by arrow 400) into a first
optical path 401 and a second optical path 402. The first optical
path 401 is substantially collinear with the light entering the
first beam splitter 212-1, and passes to the second beam splitter
212-2. The second optical path 402 is substantially perpendicular
to the light entering the first beam splitter 212-1, and passes to
the third beam splitter 212-3. In various implementations, the
first beam splitter 212-1 is a 50:50 beam splitter. In other
implementations, the first beam splitter 212-1 is a dichroic beam
splitter.
With continued reference to FIG. 10, the second beam splitter 212-2
is adjacent to the first beam splitter 212-1 (and is in direct
optical communication with the first beam splitter 212-1), and
splits the incoming light from the first beam splitter 212-1 into a
third optical path 403 and a fourth optical path 404. The third
optical path 403 is substantially collinear with the light entering
the second beam splitter 212-2, and passes through to the first
beam steering element 214-1 (see FIG. 4). The fourth optical path
is substantially perpendicular to the light entering the second
beam splitter 212-2, and passes through to the second beam steering
element 214-2. In various implementations, the second beam splitter
212-2 is a 50:50 beam splitter. In other implementations, the
second beam splitter 212-2 is a dichroic beam splitter.
The beam steering elements 214 (e.g., 214-1 . . . 214-4 shown in
FIG. 4) are configured to change the direction of the light that
enters one face of the beam steering element. Beam steering
elements 214 are any appropriate optical device that changes the
direction of light. For example, in various implementations, the
beam steering elements 214 are prisms (e.g., folding prisms,
bending prisms, etc.). In various implementations, the beam
steering elements 214 are mirrors. In various implementations, the
beam steering elements 214 are other appropriate optical devices or
combinations of devices.
Returning to FIG. 4, the first beam steering element 214-1 is
adjacent to and in direct optical communication with the second
beam splitter 212-2, and receives light from the third optical path
(e.g., the output of the second beam splitter 212-2 that is
collinear with the input to the second beam splitter 212-2). The
first beam steering element 214-1 deflects the light in a direction
that is substantially perpendicular to the fourth optical path
(and, in various implementations, perpendicular to a plane defined
by the optical paths of the beam splitters 212, e.g., the x-y
plane) and onto the first photo-sensor 210-1 coupled to the first
circuit board 206 (FIG. 3). The output of the first beam steering
element 214-1 is represented by arrow 411 (see FIG. 4).
The second beam steering element 214-2 is adjacent to and in direct
optical communication with the second beam splitter 212-2, and
receives light from the fourth optical path (e.g., the
perpendicular output of the second beam splitter 212-2). The second
beam steering element 214-2 deflects the light in a direction that
is substantially perpendicular to the third optical path (and, in
various implementations, perpendicular to a plane defined by the
optical paths of the beam splitters 212, e.g., the x-y plane) and
onto the second photo-sensor 210-2 coupled to the second circuit
board 208 (FIG. 3). The output of the second beam steering element
214-2 is represented by arrow 412 (see FIG. 4).
As noted above, the first beam splitter 212-1 passes light to the
second beam splitter 212-2 along a first optical path (as discussed
above), and to the third beam splitter 212-3 along a second optical
path.
With reference to FIG. 10, the third beam splitter 212-3 is
adjacent to the first beam splitter 212-1 (and is in direct optical
communication with the first beam splitter 212-1), and splits the
incoming light from the first beam splitter 212-1 into a fifth
optical path 405 and a sixth optical path 406. The fifth optical
path 405 is substantially collinear with the light entering the
third beam splitter 212-3, and passes through to the third beam
steering element 214-3 (see FIG. 4). The sixth optical path is
substantially perpendicular to the light entering the third beam
splitter 212-3, and passes through to the fourth beam steering
element 214-4. In various implementations, the third beam splitter
212-3 is a 50:50 beam splitter. In other implementations, the third
beam splitter 212-3 is a dichroic beam splitter.
The third beam steering element 214-3 (see FIG. 4) is adjacent to
and in direct optical communication with the third beam splitter
212-3, and receives light from the fifth optical path (e.g., the
output of the third beam splitter 212-3 that is collinear with the
input to the third beam splitter 212-3). The third beam steering
element 214-3 deflects the light in a direction that is
substantially perpendicular to the third optical path (and, in
various implementations, perpendicular to a plane defined by the
optical paths of the beam splitters 212, e.g., the x-y plane) and
onto the third photo-sensor 210-3 coupled to the first circuit
board 206 (FIG. 3). The output of the third beam steering element
214-3 is represented by arrow 413 (see FIG. 4).
The fourth beam steering element 214-4 is adjacent to and in direct
optical communication with the third beam splitter 212-3, and
receives light from the sixth optical path (e.g., the perpendicular
output of the third beam splitter 212-3). The fourth beam steering
element 214-4 deflects the light in a direction that is
substantially perpendicular to the sixth optical path (and, in
various implementations, perpendicular to a plane defined by the
optical paths of the beam splitters 212, e.g., the x-y plane) and
onto the fourth photo-sensor 210-4 coupled to the second circuit
board 208 (FIG. 3). The output of the fourth beam steering element
214-4 is represented by arrow 414 (see FIG. 4).
As shown in FIG. 4, the output paths of the first and third beam
steering elements 214-1, 214-3 are in opposite directions than the
output paths of the second and fourth beam steering elements 214-2,
214-4. Thus, the image captured by the lens assembly 104 is
projected onto the photo-sensors mounted on the opposite sides of
the image assembly 102. However, the beam steering elements 212
need not face these particular directions. Rather, any of the beam
steering elements 212 can be positioned to direct the output path
of each beam steering element 212 in any appropriate direction. For
example, in various implementations, all of the beam steering
elements 212 direct light in the same direction. In such cases, all
of the photo-sensors may be mounted on a single circuit board
(e.g., the first circuit board 206 or the second circuit board 208,
FIG. 3). Alternatively, in various implementations, one or more of
the beam steering elements 212 directs light substantially
perpendicular to the incoming light, but in substantially the same
plane defined by the optical paths of the beam splitters 212 (e.g.,
within the x-y plane). In yet other implementations, one or more
beam steering elements 214 are excluded from the imaging device,
and the corresponding photo-sensors 210 are positioned orthogonal
to the plane defined by optical paths 400-1 to 400-6.
FIG. 5A is a top schematic view of the optical assembly 102 and the
optical path assembly 204 in accordance with various
implementations, and FIG. 10 is a two-dimensional schematic
illustration of the optical paths within the optical path assembly
204. Although illustrated with a single light source 106, this
optical path assembly may also be implemented using a second light
source 107, as illustrated in FIG. 5C. Light from the lens assembly
104 enters the first beam splitter 210-1, as indicated by arrow
400. The first beam splitter 210-1 splits the incoming light (arrow
400) into a first optical path (arrow 401) that is collinear to the
incoming light (arrow 400). Light along the first optical path
(arrow 401) is passed through to the second beam splitter 210-2.
The first beam splitter 210-1 also splits the incoming light (arrow
400) into a second optical path (arrow 402) that is perpendicular
to the incoming light (arrow 400). Light along the second optical
path (arrow 402) is passed through to the third beam splitter
210-3.
Light entering the second beam splitter 210-2 (arrow 402) is
further split into a third optical path (arrow 403) that is
collinear with the incoming light (arrow 400 and/or arrow 402).
Light along the third optical path (arrow 403) is passed to the
first beam steering element 214-1 (see, e.g., FIG. 4), which steers
the light onto the first photo-sensor 210-1. As discussed above, in
various implementations, the first beam steering element 214-1
deflects the light in a direction that is perpendicular to the
light entering the second beam splitter and out of the plane
defined by the beam splitters (e.g., in a positive z-direction, or
out of the page, as shown in FIG. 5).
Light entering the second beam splitter 210-2 (arrow 402) is
further split into a fourth optical path (arrow 404) that is
perpendicular to the incoming light (arrow 400 and/or arrow 402).
Light along the fourth optical path (arrow 404) is passed to the
second beam steering element 214-2, which steers the light onto the
second photo-sensor 210-2. As discussed above, in various
implementations, the second beam steering element 214-2 deflects
the light in a direction that is perpendicular to the light
entering the second beam splitter and out of the plane defined by
the beam splitters (e.g., in a negative z-direction, or into the
page, as shown in FIG. 5).
Light entering the third beam splitter 210-3 (arrow 402) is further
split into a fifth optical path (arrow 405) that is collinear with
the light incoming into the third beam splitter 210-3 (arrow 402).
Light along the fifth optical path (arrow 405) is passed to the
third beam steering element 214-3 (see, e.g., FIG. 4), which steers
the light onto the third photo-sensor 210-3. As discussed above, in
various implementations, the third beam steering element 214-3
deflects the light in a direction that is perpendicular to the
light entering the third beam splitter and out of the plane defined
by the beam splitters (e.g., in a positive z-direction, or out of
the page, as shown in FIG. 5).
Light entering the third beam splitter 210-3 (arrow 402) is further
split into a sixth optical path (arrow 406) that is perpendicular
to the light incoming into the third beam splitter 210-3 (arrow
402). Light along the sixth optical path (arrow 406) is passed to
the fourth beam steering element 214-4, which steers the light onto
the fourth photo-sensor 210-4. As discussed above, in various
implementations, the fourth beam steering element 214-4 deflects
the light in a direction that is perpendicular to the light
entering the third beam splitter and out of the plane defined by
the beam splitters (e.g., in a negative z-direction, or into the
page, as shown in FIG. 5).
FIG. 5B is a top schematic view of the optical assembly 102 and the
optical path assembly 204 in accordance with various
implementations, and FIG. 12 is a two-dimensional schematic
illustration of the optical paths within the optical path assembly
204. Although illustrated with two light sources 106, 107, the
optical path may also be implemented with a single light source,
configured to operate in one or more operating modes (e.g., two
operating modes as described herein).
Light from the lens assembly 104 enters the first beam splitter
220-1, as indicated by arrow 600. The first beam splitter 220-1
splits the incoming light (arrow 600) into a first optical path
(arrow 601) that is perpendicular to the incoming light (arrow 600)
and a second optical path (arrow 602) that is collinear to the
incoming light (arrow 600). Light along the first optical path
(arrow 601) is passed to a beam steering element in similar manner
described above, which steers the light onto the third photo-sensor
210-3. As discussed above, in various implementations, the steering
element deflects the light in a direction that is perpendicular to
the first optical path (arrow 601) and out of the plane (e.g., in a
positive z-direction, or out of the page) toward the third
photo-sensor 210-3. Light along the second optical path (arrow 602)
is passed through to a second beam splitter 220-2.
The second beam splitter 220-2 splits the incoming light (arrow
602) into a third optical path (arrow 603) that is perpendicular to
the incoming light (arrow 602) and a fourth optical path (arrow
604) that is collinear to the incoming light (arrow 602). Light
along the third optical path (arrow 603) is passed to another beam
steering element in similar manner described above, which steers
the light onto the second photo-sensor 210-2. As discussed above,
in various implementations, the steering element deflects the light
in a direction that is perpendicular to the third optical path
(arrow 603) and out of the plane (e.g., in a negative z-direction,
or into the page) toward the second photo-sensor 210-2. Light along
the fourth optical path (arrow 604) is passed through to a third
beam splitter 220-3.
The third beam splitter 220-3 splits the incoming light (arrow 604)
into a fifth optical path (arrow 605) that is perpendicular to the
incoming light (arrow 604) and a sixth optical path (arrow 606)
that is collinear to the incoming light (arrow 604). Light along
the fifth optical path (arrow 605) is passed to another beam
steering element, which steers the light onto the fourth
photo-sensor 210-4. As discussed above, in various implementations,
the steering element deflects the light in a direction that is
perpendicular to the firth optical path (arrow 605) and out of the
plane (e.g., in a negative z-direction, or into the page) toward
the fourth photo-sensor 210-4. Light along the sixth optical path
(arrow 606) is passed to another beam steering element, which
steers the light onto the first photo-sensor 210-1. As discussed
above, in various implementations, the steering element deflects
the light in a direction that is perpendicular to the sixth optical
path (arrow 606) and out of the plane (e.g., in a positive
z-direction, or out of the page) toward the first photo-sensor
210-1.
FIG. 6 is a front schematic view of the optical assembly 102, in
accordance with various implementations. For clarity, the lens
assembly 104 and light source 106 are not shown. The lines within
the beam splitters 212 and the beam steering elements 214 further
depict the light paths described herein. For example, the line
designated by arrow 404 illustrates how the beam steering element
214-2 deflects the light received from the beam splitter 212-2 onto
the photo-sensor 210-2. Further, the line designated by arrow 402
illustrates how the beam steering element 214-3 deflects the light
received from the beam splitter 212-3 onto the photo-sensor 210-3.
Arrows 411-414 (corresponding to the optical paths indicated in
FIG. 4) further illustrate how the beam steering elements 214
direct light to their respective photo-sensors 210.
In the instant application, the geometric terms such as parallel,
perpendicular, orthogonal, coplanar, collinear, etc., are
understood to encompass orientations and/or arrangements that
substantially satisfy these geometric relationships. For example,
when a beam steering element deflects light perpendicularly, it is
understood that the beam steering element may deflect the light
substantially perpendicularly. As a more specific example, in some
cases, light may be determined to be perpendicular (or
substantially perpendicular) when the light is deflected 90+/-1
degrees from its input path. Other deviations from exact geometric
relationships are also contemplated.
As noted above, the optical assembly 102 can use various
combinations of 50:50 beam splitters and dichroic beam splitters.
In a first example, the first beam splitter 212-1, the second beam
splitter 212-2, and the third beam splitter 212-3 are all 50:50
beam splitters. An example optical assembly 102 with this selection
of beam splitters is illustrated in FIG. 10.
In a second example, the first beam splitter 212-1 is a dichroic
beam splitter, and the second beam splitter 212-2 and the third
beam splitter 212-3 are both 50:50 beam splitters. An example
optical assembly 102 with this selection of beam splitters is
illustrated in FIG. 11.
In a third example, the first beam splitter 212-1, the second beam
splitter 212-2, and the third beam splitter 212-3 are all dichroic
beam splitters. An example optical assembly 102 with this selection
of beam splitters is illustrated in FIG. 12.
FIG. 7 is a cutaway view of an implementation of imaging device
100, illustrating light paths 410 and 411, corresponding to light
emitted from light source 106 and illuminating the object being
imaged, as well as light path 400, corresponding to light
backscattered from the object.
The use of polarized illumination is advantageous because it
eliminates surface reflection from the skin and helps to eliminate
stray light reflection from off axis imaging directions.
Accordingly, in various implementations, polarized light is used to
illuminate the object being imaged. In various implementations, the
light is polarized with respect to a coordinate system relating to
the plane of incidence formed by the propagation direction of the
light (e.g., the light emitted by light source 106) and a vector
perpendicular to the plane of the reflecting surface (e.g., the
object being imaged). The component of the electric field parallel
to the plane of incidence is referred to as the p-component and the
component perpendicular to the plane is referred to as the
s-component. Accordingly, polarized light having an electric field
along the plane of incidence is "p-polarized," while polarized
light having an electric field normal to the plane is
"s-polarized."
Light can be polarized by placing a polarization filter in the path
of the light. The polarizer allows light having the same
polarization (e.g., p-polarized or s-polarized) to pass through,
while reflecting light having the opposite polarization. Because
the polarizer is passively filtering the incident beam, 50% of
non-polarized light is lost due to reflection off the polarizing
filter. In practice, therefore, a non-polarized light source must
produce twice the desired amount of polarized illuminating light,
at twice the power consumption, to account for this loss.
Advantageously, in various implementations, the imaging device
recaptures and reverses the polarity light reflected off the
polarization filter, using a polarization rotator (e.g., a
polarization rotation mirror). In various implementations, at least
95% of all of the light received by the polarizer from the at least
one light source may be illuminated onto the object.
Returning to FIG. 7, in one implementation, light emitted from
light source 106 along optical path 410 is received by polarizer
700. The portion of the light having the same polarization as
polarizer 700 (e.g., s- or p-polarization) passes through polarizer
700 and is directed, through optical window 114, onto the surface
of the object. The portion of the light having the opposite
polarization as polarizer 700 is reflected orthogonally along
optical path 411, directed to polarization rotator 702.
Polarization rotator 700 reverses the polarization of the light
(e.g., reverses the polarization to match the polarization
transmitted through polarizer 700) and reflects the light, through
optical window 114, onto the surface of the object. Polarized light
backscattered from the object, returning along optical path 400, is
captured by lens assembly 104 and is directed internal to optical
assembly 102 as described above.
In this fashion, accounting for incidental loss of light along the
optical path, substantially all the light emitted from light source
106 is projected onto the surface of the object being imaged in a
polarized manner. This eliminates the need for light source 106 to
produce twice the desired amount illuminating light, effectively
reducing the power consumption from illumination by 50%.
FIGS. 9A-9C are illustrations of framing guides projected onto the
surface of an object for focusing an image collected by an
implementation of an imaging device 100.
As noted above, in various implementations, the lens assembly 104
has a fixed focal distance. Thus, images captured by the imaging
device 100 will only be in focus if the imaging device 110 is
maintained at an appropriate distance from the object to be imaged.
In various implementations, the lens assembly 104 has a depth of
field of a certain range, such that objects falling within that
range will be suitably focused. For example, in various
implementations, the focus distance of the lens assembly 104 is 24
inches, and the depth of field is 3 inches. Thus, objects falling
anywhere from 21 to 27 inches away from the lens assembly 104 will
be suitably focused. These values are merely exemplary, and other
focus distances and depths of field are also contemplated.
Referring to FIG. 8A-8B, to facilitate accurate positioning of the
imaging device 100 with respect to the object to be imaged, the
docking station 110 includes first and second projectors 112 (e.g.,
112-1, 112-2) configured to project light (e.g., light 901, 903 in
FIGS. 8A and 8B, respectively) onto the object indicating when the
imaging device 100 is positioned at an appropriate distance from
the object to acquire a focused image. In various implementations,
with reference to FIGS. 9A-9C, the first projector 112-1 and the
second projector 112-2 are configured to project a first portion
902-1 and a second portion 902-2 of a shape 902 onto the object
(FIGS. 9A-9C), respectively. The first portion of the shape 902-1
and the second portion of the shape 902-1 are configured to
converge to form the shape 902 when the lens 104 is positioned at a
predetermined distance from the object, the predetermined distance
corresponding to a focus distance of the lens.
In one implementation, the framing guides converge to form a closed
rectangle on the surface of the object when the lens of the imaging
device 100 is positioned at predetermined distance from the object
corresponding to the focus distance of the lens (FIG. 9C). When the
lens of the imaging device 100 is positioned at distance from the
object that is less than the predetermined distance, the framing
guides remain separated (FIG. 9A). When the lens of the imaging
device 100 is positioned at distance from the object that is
greater than the predetermined distance, the framing guides cross
each other (FIG. 9B).
In various implementations, the framing guides represent all or
substantially all the area of the object that will be captured by
the imaging device 100. In various implementations, at least all of
the object that falls inside the framing guides will be captured by
the imaging device 100.
In various implementations, as illustrated in FIG. 8B, first
projector 112-1 and second projector 112-2 are each configured to
project a spot onto the object (e.g., spots 904-1 and 904-2,
illustrated in FIG. 9D), such that the spots converge (e.g., at
spot 904 in FIG. 9E) when the lens 104 is positioned at a
predetermined distance from the object, the predetermined distance
corresponding to a focus distance of the lens. When the lens of the
imaging device 100 is positioned at distance from the object that
is less than or greater than the predetermined distance, the
projected spots diverge from each other (FIG. 9D).
FIG. 1B illustrates another imaging device 100, in accordance with
various implementations, similar to that shown in FIG. 1A but
including an integrated body 101 that resembles a digital
single-lens reflex (DSLR) camera in that the body has a
forward-facing lens assembly 104, and a rearward facing display
122. The DSLR-type housing allows a user to easily hold imaging
device 100, aim it toward a patient and the region of interest
(e.g., the skin of the patient), and position the device at an
appropriate distance from the patient. One will appreciate that the
implementation of FIG. 1B, may incorporate the various features
described above and below in connection with the device of FIG.
1A.
In various implementations, and similar to the device described
above, the imaging device 100 illustrated in FIG. 1B includes an
optical assembly having light sources 106 and 107 for illuminating
the surface of an object (e.g., the skin of a subject) and a lens
assembly 104 for collecting light reflected and/or back scattered
from the object.
In various implementations, and also similar to the device
described above, the imaging device of FIG. 1B includes first and
second projectors 112-1 and 112-2 configured to project light onto
the object indicating when the imaging device 100 is positioned at
an appropriate distance from the object to acquire a focused image.
As noted above, this may be particularly useful where the lens
assembly 104 has a fixed focal distance, such that the image cannot
be brought into focus by manipulation of the lens assembly. As
shown in FIG. 1B, the projectors are mounted on a forward side of
body 101.
In various implementations, the body 101 substantially encases and
supports the light sources 106 and 107 and the lens assembly 104 of
the optical assembly, along with the first and second projectors
112-1 and 112-2 and the display 122.
FIGS. 13 and 14 collectively illustrate another configuration for
imaging device 100, in accordance with various implementations,
similar to that shown in FIG. 1B but including more detail
regarding an embodiment of integrated body 101 and forward-facing
lens assembly 104, and a rearward facing display 122. The housing
101 allows a user to easily hold imaging device 100, aim it toward
a patient and the region of interest (e.g., the skin of the
patient), and position the device at an appropriate distance from
the patient. One will appreciate that the implementation of FIGS.
13 and 14 may incorporate the various features described herein in
connection with the device of FIGS. 1A and 1B.
In various implementations, and similar to the device described
above, the imaging device 100 illustrated in FIGS. 13 and 14
includes an optical assembly having light sources 106 and 107 for
illuminating the surface of an object (e.g., the skin of a subject)
and a lens assembly 104 for collecting light reflected and/or back
scattered from the object.
In various implementations, and also similar to the device
described in FIGS. 1A and 1B, the imaging device of FIG. 13
includes first and second projectors 112-1 and 112-2 configured to
project light onto the object indicating when the imaging device
100 is positioned at an appropriate distance from the object to
acquire a focused image. As noted above, this may be particularly
useful where the lens assembly 104 has a fixed focus distance, such
that the image cannot be brought into focus by manipulation of the
lens assembly. As shown in FIG. 13, the projectors are mounted on a
forward side of body 101.
In various implementations, the body 101 substantially encases and
supports the light sources 106 and 107 and the lens assembly 104 of
the optical assembly, along with the first and second projectors
112-1 and 112-2. In various implementations, the imaging device 101
of FIG. 13 includes a live-view camera 103 and a remote thermometer
105.
Exemplary Optical Configurations
In one implementation, the imaging device 100 is configured to
detect a set of spectral bands suitable for determining the
oxyhemoglobin and deoxyhemoglobin distribution in a tissue. In a
specific implementation, this is achieved by capturing images of
the tissue of interest at eight different spectral bands. The
images are captured in two exposures of four photo-sensors 210,
each photo-sensor covered by a unique dual band pass filter 216. In
one implementation, the imaging device 100 has a first light source
106 configured to illuminate the tissue of interest with light
including exactly four of the eight spectral bands, where each dual
band pass filter 216 has exactly one pass band matching a spectral
band in the four spectral bands emitted from light source 106. The
imaging device has a second light source 107 configured to
illuminate the tissue of interest with light including the other
four spectral bands of the set of eight spectral bands (e.g., but
not the first four spectral bands), where each dual band pass
filter 216 has exactly one pass band matching a spectral band in
the four spectral bands emitted from light source 107.
In one implementation, the set of eight spectral bands includes
spectral bands having central wavelengths of: 510.+-.5 nm, 530.+-.5
nm, 540.+-.5 nm, 560.+-.5 nm, 580.+-.5 nm, 590.+-.5 nm, 620.+-.5
nm, and 660.+-.5 nm, and each spectral band has a full width at
half maximum of less than 15 nm. In a related implementation, the
set of eight spectral bands includes spectral bands having central
wavelengths of: 510.+-.4 nm, 530.+-.4 nm, 540.+-.4 nm, 560.+-.4 nm,
580.+-.4 nm, 590.+-.4 nm, 620.+-.4 nm, and 660.+-.4 nm, and each
spectral band has a full width at half maximum of less than 15 nm.
In a related implementation, the set of eight spectral bands
includes spectral bands having central wavelengths of: 510.+-.3 nm,
530.+-.3 nm, 540.+-.3 nm, 560.+-.3 nm, 580.+-.3 nm, 590.+-.3 nm,
620.+-.3 nm, and 660.+-.3 nm, and each spectral band has a full
width at half maximum of less than 15 nm. In a related
implementation, the set of eight spectral bands includes spectral
bands having central wavelengths of: 510.+-.2 nm, 530.+-.2 nm,
540.+-.2 nm, 560.+-.2 nm, 580.+-.2 nm, 590.+-.2 nm, 620.+-.2 nm,
and 660.+-.2 nm, and each spectral band has a full width at half
maximum of less than 15 nm. In a related implementation, the set of
eight spectral bands includes spectral bands having central
wavelengths of: 510.+-.1 nm, 530.+-.1 nm, 540.+-.1 nm, 560.+-.1 nm,
580.+-.1 nm, 590.+-.1 nm, 620.+-.1 nm, and 660.+-.1 nm, and each
spectral band has a full width at half maximum of less than 15 nm.
In a related implementation, the set of eight spectral bands
includes spectral bands having central wavelengths of: 510 nm, 530
nm, 540 nm, 560 nm, 580 nm, 590 nm, 620 nm, and 660 nm, and each
spectral band has a full width at half maximum of about 10 nm.
In one implementation, dual band filters having spectral pass bands
centered at: (i) 520.+-.5 and 590.+-.5, (ii) 540.+-.5 and 610.+-.5,
(iii) 560.+-.5 and 620.+-.5, and (iv) 580.+-.5 and 640.+-.5 are
placed in front of photo-sensors configured to detect this
particular set of wavelengths. In one implementation, the imaging
device has a light source 106 configured to illuminate a tissue of
interest with light having wavelengths from 450-585 nm in a first
operation mode and light having wavelengths from 585-650 nm in a
second operation mode. In one implementation, the imaging device
has a light source 106 configured to illuminate a tissue of
interest with light having wavelengths from 450-585 nm, and a
second light source 107 configured to illuminate the tissue of
interest with light having wavelengths from 585-650 nm. In still
another implementation, the imaging device has a light source 106
configured to illuminate a tissue of interest with light having
wavelengths 520, 540, 560 and 640 but not wavelengths 580, 590, 610
and 620 and a second light source 107 configured to illuminate the
tissue of interest with light having wavelengths 580, 590, 610, and
620 but not wavelengths 520, 540, 560 and 640.
In one implementation, dual band filters having spectral pass bands
centered at: (i) 520.+-.5 and 560.+-.5, (ii) 540.+-.5 and 580.+-.5,
(iii) 590.+-.5 and 620.+-.5, and (iv) 610 and 640.+-.5 are placed
in front of photo-sensors configured to detect this particular set
of wavelengths. In one implementation, the imaging device has a
light source 106 configured to illuminate a tissue of interest with
light having wavelengths from 450-550 nm and from 615-650 nm in a
first operation mode and light having wavelengths from 550-615 nm
in a second operation mode. In one implementation, the imaging
device has a light source 106 configured to illuminate a tissue of
interest with light having wavelengths from 450-550 nm and from
615-650 nm, and a second light source 107 configured to illuminate
the tissue of interest with light having wavelengths from 585-650
nm.
In one implementation, dual band filters having spectral pass bands
centered at: (i) 520.+-.5 and 560.+-.5, (ii) 540.+-.5 and 610.+-.5,
(iii) 590.+-.5 and 620.+-.5, and (iv) 580 and 640.+-.5 are placed
in front of photo-sensors configured to detect this particular set
of wavelengths. In one implementation, the imaging device has a
light source 106 configured to illuminate a tissue of interest with
light having wavelengths from 450-530 nm and from 600-650 nm in a
first operation mode and light having wavelengths from 530-600 nm
in a second operation mode. In one implementation, the imaging
device has a light source 106 configured to illuminate a tissue of
interest with light having wavelengths from 450-530 nm and from
600-650 nm, and a second light source 107 configured to illuminate
the tissue of interest with light having wavelengths from
530-600.
In one implementation, the set of eight spectral bands includes
spectral bands having central wavelengths of: 520.+-.5 nm, 540.+-.5
nm, 560.+-.5 nm, 580.+-.5 nm, 590.+-.5 nm, 610.+-.5 nm, 620.+-.5
nm, and 640.+-.5 nm, and each spectral band has a full width at
half maximum of less than 15 nm. In a related implementation, the
set of eight spectral bands includes spectral bands having central
wavelengths of: 520.+-.4 nm, 540.+-.4 nm, 560.+-.4 nm, 580.+-.4 nm,
590.+-.4 nm, 610.+-.4 nm, 620.+-.4 nm, and 640.+-.4 nm, and each
spectral band has a full width at half maximum of less than 15 nm.
In a related implementation, the set of eight spectral bands
includes spectral bands having central wavelengths of: 520.+-.3 nm,
540.+-.3 nm, 560.+-.3 nm, 580.+-.3 nm, 590.+-.3 nm, 610.+-.3 nm,
620.+-.3 nm, and 640.+-.3 nm, and each spectral band has a full
width at half maximum of less than 15 nm. In a related
implementation, the set of eight spectral bands includes spectral
bands having central wavelengths of: 520.+-.2 nm, 540.+-.2 nm,
560.+-.2 nm, 580.+-.2 nm, 590.+-.2 nm, 610.+-.2 nm, 620.+-.2 nm,
and 640.+-.2 nm, and each spectral band has a full width at half
maximum of less than 15 nm. In a related implementation, the set of
eight spectral bands includes spectral bands having central
wavelengths of: 520.+-.1 nm, 540.+-.1 nm, 560.+-.1 nm, 580.+-.1 nm,
590.+-.1 nm, 610.+-.1 nm, 620.+-.1 nm, and 640.+-.1 nm, and each
spectral band has a full width at half maximum of less than 15 nm.
In a related implementation, the set of eight spectral bands
includes spectral bands having central wavelengths of: 520 nm, 540
nm, 560 nm, 580 nm, 590 nm, 610 nm, 620 nm, and 640 nm, and each
spectral band has a full width at half maximum of about 10 nm.
In one implementation, the set of eight spectral bands includes
spectral bands having central wavelengths of: 500.+-.5 nm, 530.+-.5
nm, 545.+-.5 nm, 570.+-.5 nm, 585.+-.5 nm, 600.+-.5 nm, 615.+-.5
nm, and 640.+-.5 nm, and each spectral band has a full width at
half maximum of less than 15 nm. In a related implementation, the
set of eight spectral bands includes spectral bands having central
wavelengths of: 500.+-.4 nm, 530.+-.4 nm, 545.+-.4 nm, 570.+-.4 nm,
585.+-.4 nm, 600.+-.4 nm, 615.+-.4 nm, and 640.+-.4 nm, and each
spectral band has a full width at half maximum of less than 15 nm.
In a related implementation, the set of eight spectral bands
includes spectral bands having central wavelengths of: 500.+-.3 nm,
530.+-.3 nm, 545.+-.3 nm, 570.+-.3 nm, 585.+-.3 nm, 600.+-.3 nm,
615.+-.3 nm, and 640.+-.3 nm, and each spectral band has a full
width at half maximum of less than 15 nm. In a related
implementation, the set of eight spectral bands includes spectral
bands having central wavelengths of: 500.+-.2 nm, 530.+-.2 nm,
545.+-.2 nm, 570.+-.2 nm, 585.+-.2 nm, 600.+-.2 nm, 615.+-.2 nm,
and 640.+-.2 nm, and each spectral band has a full width at half
maximum of less than 15 nm. In a related implementation, the set of
eight spectral bands includes spectral bands having central
wavelengths of: 500.+-.1 nm, 530.+-.1 nm, 545.+-.1 nm, 570.+-.1 nm,
585.+-.1 nm, 600.+-.1 nm, 615.+-.1 nm, and 640.+-.1 nm, and each
spectral band has a full width at half maximum of less than 15 nm.
In a related implementation, the set of eight spectral bands
includes spectral bands having central wavelengths of: 500 nm, 530
nm, 545 nm, 570 nm, 585 nm, 600 nm, 615 nm, and 640 nm, and each
spectral band has a full width at half maximum of about 10 nm.
In other implementations, the imaging devices described here are
configured for imaging more or less than eight spectral bands. For
example, in some implementations, the imaging device is configured
for imaging 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,
18, 19, 20, 21, 22, 23, 24, or more spectral bands. For example,
imaging devices including 7 beam splitters and 8 photo-sensors can
be configured according to the principles described herein to
capture 8 images simultaneously, 16 images in two exposures (e.g.,
by placing dual band pass filters in from of each photosensor), and
24 images in three exposures (e.g., by placing triple band pass
filters in front of each photosensor). In fact, the number of
spectral band passes that can be imaged using the principles
disclosed herein is only constrained by any desired size of the
imager, desired exposure times, and light sources employed. Of
course, one or more photo-sensors may not be used in any given
exposure. For example, in a imaging device employing four photo
sensors and three beam splitters, seven images can be captured in
two exposures by not utilizing one of the photo-sensors in one of
the exposures. Thus, imaging devices employing any combination of
light sources (e.g., 1, 2, 3, 4, or more), beam splitters (e.g., 1,
2, 3, 4, 5, 6, 7, or more), and photo-sensors (e.g., 1, 2, 3, 4, 5,
6, 7, 8, or more) are contemplated.
Optimization of Exposure Time
Many advantages of the imaging systems and methods described herein
are derived, at least in part, from the use of in-band illumination
and detection across multiple spectral bands. For example, in-band
illumination allows for greater signal-to-noise ratio and reduced
exposure times, which in turn results in lower power consumption,
reduced misalignment due to movement of the subject, and reduced
computational burden when processing the resulting hyperspectral
data cubes.
These advantages can be further enhanced by minimizing the exposure
time (e.g., shutter speed) needed to provide a suitable
signal-to-noise ratio at each wavelength imaged. The minimum
exposure time needed to resolve a suitable image at each wavelength
will depend upon, at least, the sensitivity of the optical detector
for the particular wavelength, the characteristics and intensity of
ambient light present when acquiring images, and the concentration
of melanin in the skin/tissue being imaged.
In one embodiment, the imaging systems described herein
advantageously reduces the total amount of time required to collect
a complete image series by determining the specific exposure time
needed to resolve each sub-image of the image series. Each image in
the image series is collected at a different spectral band and,
because of this, the amount of time needed to resolve each
sub-image will vary as a function of wavelength. In some
embodiments, this variance is advantageously taken into account so
that an image requiring less time, because of their acquisition
wavelengths or wavelength bands, are allotted shorter exposure
times whereas images that require more time because of their
acquisition wavelengths or wavelength bands, are allotted shorter
exposure times. This novel improvement affords a faster overall
exposure time because each of images in the series of images is
only allocated an amount of time needed for full exposure, rather
than a "one size fits all" exposure time. This also reduces the
power requirement of the imaging device, because the illumination,
which requires a large amount of power, is shortened. In a specific
embodiment, non-transitory instructions encoded by the imager in
non-transient memory determine the minimal exposure time required
for image acquisition at each spectral band acquired by the imaging
system.
In some embodiments, the methods and systems described herein
include executable instructions for identifying a plurality of
baseline exposure times, each respective baseline exposure time in
the plurality of baseline exposure times representing an exposure
time for resolving a respective image, in the series of images of
the tissue being collected. A first baseline exposure time for a
first image is different than a second baseline exposure time of a
second image in the plurality of images.
In one embodiment, a method is provided for acquiring an image
series of a tissue of a patient, including selecting a plurality of
spectral bands for acquiring an image series of a tissue,
identifying minimum exposure times for resolving an image of the
tissue at each spectral band, identifying at least one factor
affecting one of more minimum exposure times, adjusting the minimum
exposure times based on the identified factors, and acquiring a
series of images of the tissue using the adjusted minimum exposure
times.
In some embodiments, the minimum exposure times are based on
baseline illumination of the tissue and/or the sensitivity of an
optical detector acquiring the image.
In some embodiments, the factor affecting the minimal exposure time
is one or more of illumination provided by a device used to acquire
the image series, ambient light, and concentration of melanin in
the tissue.
Hyperspectral Imaging
Hyperspectral and multispectral imaging are related techniques in
larger class of spectroscopy commonly referred to as spectral
imaging or spectral analysis. Typically, hyperspectral imaging
relates to the acquisition of a plurality of images, each image
representing a narrow spectral band collected over a continuous
spectral range, for example, 5 or more (e.g., 5, 10, 15, 20, 25,
30, 40, 50, or more) spectral bands having a FWHM bandwidth of 1 nm
or more each (e.g., 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 10 nm, 20 nm or
more), covering a contiguous spectral range (e.g., from 400 nm to
800 nm). In contrast, multispectral imaging relates to the
acquisition of a plurality of images, each image representing a
narrow spectral band collected over a discontinuous spectral
range.
For the purposes of the present disclosure, the terms
"hyperspectral" and "multispectral" are used interchangeably and
refer to a plurality of images, each image representing a narrow
spectral band (having a FWHM bandwidth of between 10 nm and 30 nm,
between 5 nm and 15 nm, between 5 nm and 50 nm, less than 100 nm,
between 1 and 100 nm, etc.), whether collected over a continuous or
discontinuous spectral range. For example, in various
implementations, wavelengths 1-N of a hyperspectral data cube
1336-1 are contiguous wavelengths or spectral bands covering a
contiguous spectral range (e.g., from 400 nm to 800 nm). In other
implementations, wavelengths 1-N of a hyperspectral data cube
1336-1 are non-contiguous wavelengths or spectral bands covering a
non-contiguous spectral ranges (e.g., from 400 nm to 440 nm, from
500 nm to 540 nm, from 600 nm to 680 nm, and from 900 to 950
nm).
As used herein, "narrow spectral range" refers to a continuous span
of wavelengths, typically consisting of a FWHM spectral band of no
more than about 100 nm. In certain embodiments, narrowband
radiation consists of a FWHM spectral band of no more than about 75
nm, 50 nm, 40 nm, 30 nm, 25 nm, 20 nm, 15 nm, 10 nm, 5 nm, 4 nm, 3
nm, 2 nm, 1 nm, or less. In various implementations, wavelengths
imaged by the methods and devices disclosed herein are selected
from one or more of the visible, near-infrared, short-wavelength
infrared, mid-wavelength infrared, long-wavelength infrared, and
ultraviolet (UV) spectrums.
By "broadband" it is meant light that includes component
wavelengths over a substantial portion of at least one band, for
example, over at least 20%, or at least 30%, or at least 40%, or at
least 50%, or at least 60%, or at least 70%, or at least 80%, or at
least 90%, or at least 95% of the band, or even the entire band,
and optionally includes component wavelengths within one or more
other bands. A "white light source" is considered to be broadband,
because it extends over a substantial portion of at least the
visible band. In certain embodiments, broadband light includes
component wavelengths across at least 100 nm of the electromagnetic
spectrum. In other embodiments, broadband light includes component
wavelengths across at least 150 nm, 200 nm, 250 nm, 300 nm, 400 nm,
500 nm, 600 nm, 700 nm, 800 nm, or more of the electromagnetic
spectrum.
By "narrowband" it is meant light that includes components over
only a narrow spectral region, for example, less than 20%, or less
than 15%, or less than 10%, or less than 5%, or less than 2%, or
less than 1%, or less than 0.5% of a single band. Narrowband light
sources need not be confined to a single band, but can include
wavelengths in multiple bands. A plurality of narrowband light
sources may each individually generate light within only a small
portion of a single band, but together may generate light that
covers a substantial portion of one or more bands, for example, may
together constitute a broadband light source. In certain
embodiments, broadband light includes component wavelengths across
no more than 100 nm of the electromagnetic spectrum (e.g., has a
spectral bandwidth of no more than 100 nm). In other embodiments,
narrowband light has a spectral bandwidth of no more than 90 nm, 80
nm, 75 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30 nm, 25 nm, 20 nm, 15 nm,
10 nm, 5 nm, or less of the electromagnetic spectrum.
As used herein, the "spectral bandwidth" of a light source refers
to the span of component wavelengths having an intensity that is at
least half of the maximum intensity, otherwise known as "full width
at half maximum" (FWHM) spectral bandwidth. Many light emitting
diodes (LEDs) emit radiation at more than a single discreet
wavelength, and are thus narrowband emitters. Accordingly, a
narrowband light source can be described as having a
"characteristic wavelength" or "center wavelength," for example,
the wavelength emitted with the greatest intensity, as well as a
characteristic spectral bandwidth, for example, the span of
wavelengths emitted with an intensity of at least half that of the
characteristic wavelength.
By "coherent light source" it is meant a light source that emits
electromagnetic radiation of a single wavelength in phase. Thus, a
coherent light source is a type of narrowband light source with a
spectral bandwidth of less than 1 nm. Non-limiting examples of
coherent light sources include lasers and laser-type LEDs.
Similarly, an incoherent light source emits electromagnetic
radiation having a spectral bandwidth of more than 1 nm and/or is
not in phase. In this regard, incoherent light can be either
narrowband or broadband light, depending on the spectral bandwidth
of the light.
Examples of suitable broadband light sources 106 include, without
limitation, incandescent lights such as a halogen lamp, xenon lamp,
a hydrargyrum medium-arc iodide lamp, and a broadband light
emitting diode (LED). In some embodiments, a standard or custom
filter is used to balance the light intensities at different
wavelengths to raise the signal level of certain wavelength or to
select for a narrowband of wavelengths. Broadband illumination of a
subject is particularly useful when capturing a color image of the
subject or when focusing the hyperspectral/multispectral imaging
system.
Examples of suitable narrowband, incoherent light sources 106
include, without limitation, a narrow band light emitting diode
(LED), a superluminescent diode (SLD) (see, Redding, B. et al,
"Speckle-free laser imaging", arVix: 1110.6860 (2011), the content
of which is hereby incorporated herein by reference in its entirety
for all purposes), a random laser, and a broadband light source
covered by a narrow band-pass filter. Examples of suitable
narrowband, coherent light sources 104 include, without limitation,
lasers and laser-type light emitting diodes. While both coherent
and incoherent narrowband light sources 104 can be used in the
imaging systems described herein, coherent illumination is less
well suited for full-field imaging due to speckle artifacts that
corrupt image formation (see, Oliver, B. M., "Sparkling spots and
random diffraction", Proc IEEE 51, 220-221 (1963)).
Hyperspectral Medical Imaging
Various implementations of the present disclosure provide for
systems and methods useful for hyperspectral/multispectral medical
imaging (HSMI). HSMI relies upon distinguishing the interactions
that occur between light at different wavelengths and components of
the human body, especially components located in or just under the
skin. For example, it is well known that deoxyhemoglobin absorbs a
greater amount of light at 700 nm than does water, while water
absorbs a much greater amount of light at 1200 nm, as compared to
deoxyhemoglobin. By measuring the absorbance of a two-component
system consisting of deoxyhemoglobin and water at 700 nm and 1200
nm, the individual contribution of deoxyhemoglobin and water to the
absorption of the system, and thus the concentrations of both
components, can readily be determined By extension, the individual
components of more complex systems (e.g., human skin) can be
determined by measuring the absorption of a plurality of
wavelengths of light reflected or backscattered off of the
system.
The particular interactions between the various wavelengths of
light measured by hyperspectral/multispectral imaging and each
individual component of the system (e.g., skin) produces
hyperspectral/multispectral signature, when the data is constructed
into a hyperspectral/multispectral data cube. Specifically,
different regions (e.g., different regions of interest or ROI on a
single subject or different ROIs from different subjects) interact
differently with light depending on the presence of, e.g., a
medical condition in the region, the physiological structure of the
region, and/or the presence of a chemical in the region. For
example, fat, skin, blood, and flesh all interact with various
wavelengths of light differently from one another. A given type of
cancerous lesion interacts with various wavelengths of light
differently from normal skin, from non-cancerous lesions, and from
other types of cancerous lesions. Likewise, a given chemical that
is present (e.g., in the blood, or on the skin) interacts with
various wavelengths of light differently from other types of
chemicals. Thus, the light obtained from each illuminated region of
a subject has a spectral signature based on the characteristics of
the region, which signature contains medical information about that
region.
The structure of skin, while complex, can be approximated as two
separate and structurally different layers, namely the epidermis
and dermis. These two layers have very different scattering and
absorption properties due to differences of composition. The
epidermis is the outer layer of skin. It has specialized cells
called melanocytes that produce melanin pigments. Light is
primarily absorbed in the epidermis, while scattering in the
epidermis is considered negligible. For further details, see G. H.
Findlay, "Blue Skin," British Journal of Dermatology 83(1), 127-134
(1970), the content of which is incorporated herein by reference in
its entirety for all purposes.
The dermis has a dense collection of collagen fibers and blood
vessels, and its optical properties are very different from that of
the epidermis. Absorption of light of a bloodless dermis is
negligible. However, blood-born pigments like oxy- and
deoxyhemoglobin and water are major absorbers of light in the
dermis. Scattering by the collagen fibers and absorption due to
chromophores in the dermis determine the depth of penetration of
light through skin.
Light used to illuminate the surface of a subject will penetrate
into the skin. The extent to which the light penetrates will depend
upon the wavelength of the particular radiation. For example, with
respect to visible light, the longer the wavelength, the farther
the light will penetrate into the skin. For example, only about 32%
of 400 nm violet light penetrates into the dermis of human skin,
while greater than 85% of 700 nm red light penetrates into the
dermis or beyond (see, Capinera J. L., "Photodynamic Action in Pest
Control and Medicine", Encyclopedia of Entomology, 2nd Edition,
Springer Science, 2008, pp. 2850-2862, the content of which is
hereby incorporated herein by reference in its entirety for all
purposes). For purposes of the present disclosure, when referring
to "illuminating a tissue," "reflecting light off of the surface,"
and the like, it is meant that radiation of a suitable wavelength
for detection is backscattered from a tissue of a subject,
regardless of the distance into the subject the light travels. For
example, certain wavelengths of infra-red radiation penetrate below
the surface of the skin, thus illuminating the tissue below the
surface of the subject.
Briefly, light from the illuminator(s) on the systems described
herein penetrates the subject's superficial tissue and photons
scatter in the tissue, bouncing inside the tissue many times. Some
photons are absorbed by oxygenated hemoglobin molecules at a known
profile across the spectrum of light. Likewise for photons absorbed
by de-oxygenated hemoglobin molecules. The images resolved by the
optical detectors consist of the photons of light that scatter back
through the skin to the lens subsystem. In this fashion, the images
represent the light that is not absorbed by the various
chromophores in the tissue or lost to scattering within the tissue.
In some embodiments, light from the illuminators that does not
penetrate the surface of the tissue is eliminated by use of
polarizers. Likewise, some photons bounce off the surface of the
skin into air, like sunlight reflecting off a lake.
Accordingly, different wavelengths of light may be used to examine
different depths of a subject's skin tissue. Generally, high
frequency, short-wavelength visible light is useful for
investigating elements present in the epidermis, while lower
frequency, long-wavelength visible light is useful for
investigating both the epidermis and dermis. Furthermore, certain
infra-red wavelengths are useful for investigating the epidermis,
dermis, and subcutaneous tissues.
In the visible and near-infrared (VNIR) spectral range and at low
intensity irradiance, and when thermal effects are negligible,
major light-tissue interactions include reflection, refraction,
scattering and absorption. For normal collimated incident
radiation, the regular reflection of the skin at the air-tissue
interface is typically only around 4%-7% in the 250-3000 nanometer
(nm) wavelength range. For further details, see Anderson, R. R. et
al., "The Optics of Human Skin", Journal of Investigative
Dermatology, 77, pp. 13-19, 1981, the content of which is hereby
incorporated by reference in its entirety for all purposes. When
neglecting the air-tissue interface reflection and assuming total
diffusion of incident light after the stratum corneum layer, the
steady state VNIR skin reflectance can be modeled as the light that
first survives the absorption of the epidermis, then reflects back
toward the epidermis layer due the isotropic scattering in the
dermis layer, and then finally emerges out of the skin after going
through the epidermis layer again.
Accordingly, the systems and methods described herein can be used
to diagnose and characterize a wide variety of medical conditions.
In one embodiment, the concentration of one or more skin or blood
component is determined in order to evaluate a medical condition in
a patient. Non-limiting examples of components useful for medical
evaluation include: deoxyhemoglobin levels, oxyhemoglobin levels,
total hemoglobin levels, oxygen saturation, oxygen perfusion,
hydration levels, total hematocrit levels, melanin levels, collagen
levels, and bilirubin levels. Likewise, the pattern, gradient, or
change over time of a skin or blood component can be used to
provide information on the medical condition of the patient.
Non-limiting examples of conditions that can be evaluated by
hyperspectral/multispectral imaging include: tissue ischemia, ulcer
formation, ulcer progression, pressure ulcer formation, pressure
ulcer progression, diabetic foot ulcer formation, diabetic foot
ulcer progression, venous stasis, venous ulcer disease, peripheral
artery disease, atherosclerosis, infection, shock, cardiac
decompensation, respiratory insufficiency, hypovolemia, the
progression of diabetes, congestive heart failure, sepsis,
dehydration, hemorrhage, hemorrhagic shock, hypertension, cancer
(e.g., detection, diagnosis, or typing of tumors or skin lesions),
retinal abnormalities (e.g., diabetic retinopathy, macular
degeneration, or corneal dystrophy), skin wounds, burn wounds,
exposure to a chemical or biological agent, and an inflammatory
response.
In various embodiments, the systems and methods described herein
are used to evaluate tissue oximetery and correspondingly, medical
conditions relating to patient health derived from oxygen
measurements in the superficial vasculature. In certain
embodiments, the systems and methods described herein allow for the
measurement of oxygenated hemoglobin, deoxygenated hemoglobin,
oxygen saturation, and oxygen perfusion. Processing of these data
provide information to assist a physician with, for example,
diagnosis, prognosis, assignment of treatment, assignment of
surgery, and the execution of surgery for conditions such as
critical limb ischemia, diabetic foot ulcers, pressure ulcers,
peripheral vascular disease, surgical tissue health, etc.
In various embodiments, the systems and methods described herein
are used to evaluate diabetic and pressure ulcers. Development of a
diabetic foot ulcer is commonly a result of a break in the barrier
between the dermis of the skin and the subcutaneous fat that
cushions the foot during ambulation. This rupture can lead to
increased pressure on the dermis, resulting in tissue ischemia and
eventual death, and ultimately manifesting in the form of an ulcer
(Frykberg R. G. et al., "Role of neuropathy and high foot pressures
in diabetic foot ulceration", Diabetes Care, 21(10),
1998:1714-1719). Measurement of oxyhemoglobin, deoxyhemoglobin,
and/or oxygen saturation levels by hyperspectral/multispectral
imaging can provide medical information regarding, for example: a
likelihood of ulcer formation at an ROI, diagnosis of an ulcer,
identification of boundaries for an ulcer, progression or
regression of ulcer formation, a prognosis for healing of an ulcer,
the likelihood of amputation resulting from an ulcer. Further
information on hyperspectral/multispectral methods for the
detection and characterization of ulcers, e.g., diabetic foot
ulcers, are found in U.S. Patent Application Publication No.
2007/0038042, and Nouvong, A. et al., "Evaluation of diabetic foot
ulcer healing with hyperspectral imaging of oxyhemoglobin and
deoxyhemoglobin", Diabetes Care. 2009 November; 32(11):2056-2061,
the contents of which are hereby incorporated herein by reference
in their entireties for all purposes.
Other examples of medical conditions include, but are not limited
to: tissue viability (e.g., whether tissue is dead or living,
and/or whether it is predicted to remain living); tissue ischemia;
malignant cells or tissues (e.g., delineating malignant from benign
tumors, dysplasias, precancerous tissue, metastasis); tissue
infection and/or inflammation; and/or the presence of pathogens
(e.g., bacterial or viral counts). Various embodiments may include
differentiating different types of tissue from each other, for
example, differentiating bone from flesh, skin, and/or vasculature.
Various embodiments may exclude the characterization of
vasculature.
In various embodiments, the systems and methods provided herein can
be used during surgery, for example to determine surgical margins,
evaluate the appropriateness of surgical margins before or after a
resection, evaluate or monitor tissue viability in near-real time
or real-time, or to assist in image-guided surgery. For more
information on the use of hyperspectral/multispectral imaging
during surgery, see, Holzer M. S. et al., "Assessment of renal
oxygenation during partial nephrectomy using hyperspectral
imaging", J Urol. 2011 August; 186(2):400-4; Gibbs-Strauss S. L. et
al., "Nerve-highlighting fluorescent contrast agents for
image-guided surgery", Mol Imaging. 2011 April; 10(2):91-101; and
Panasyuk S. V. et al., "Medical hyperspectral imaging to facilitate
residual tumor identification during surgery", Cancer Biol Ther.
2007 March; 6(3):439-46, the contents of which are hereby
incorporated herein by reference in their entirety for all
purposes.
For more information on the use of hyperspectral/multispectral
imaging in medical assessments, see, for example: Chin J. A. et
al., J Vasc Surg. 2011 December; 54(6):1679-88; Khaodhiar L. et
al., Diabetes Care 2007; 30:903-910; Zuzak K. J. et al., Anal Chem.
2002 May 1; 74(9):2021-8; Uhr J. W. et al., Transl Res. 2012 May;
159(5):366-75; Chin M. S. et al., J Biomed Opt. 2012 February;
17(2):026010; Liu Z. et al., Sensors (Basel). 2012; 12(1):162-74;
Zuzak K. J. et al., Anal Chem. 2011 Oct. 1; 83(19):7424-30; Palmer
G. M. et al., J Biomed Opt. 2010 November-December; 15(6):066021;
Jafari-Saraf and Gordon, Ann Vasc Surg. 2010 August; 24(6):741-6;
Akbari H. et al., IEEE Trans Biomed Eng. 2010 August; 57(8):2011-7;
Akbari H. et al., Conf Proc IEEE Eng Med Biol Soc. 2009:1461-4;
Akbari H. et al., Conf Proc IEEE Eng Med Biol Soc. 2008:1238-41;
Chang S. K. et al., Clin Cancer Res. 2008 Jul. 1; 14(13):4146-53;
Siddiqi A. M. et al., Cancer. 2008 Feb. 25; 114(1):13-21; Liu Z. et
al., Appl Opt. 2007 Dec. 1; 46(34):8328-34; Zhi L. et al., Comput
Med Imaging Graph. 2007 December; 31(8):672-8; Khaodhiar L. et al.,
Diabetes Care. 2007 April; 30(4):903-10; Ferris D. G. et al., J Low
Genit Tract Dis. 2001 April; 5(2):65-72; Greenman R. L. et al.,
Lancet. 2005 Nov. 12; 366(9498):1711-7; Sorg B. S. et al., J Biomed
Opt. 2005 July-August; 10(4):44004; Gillies R. et al., and Diabetes
Technol Ther. 2003; 5(5):847-55, the contents of which are hereby
incorporated herein by reference in their entirety for all
purposes.
EXEMPLARY EMBODIMENTS
Provided in this section are nonlimiting exemplary embodiments in
accordance with the present disclosure.
Embodiment 1
An imaging device, comprising a lens disposed along an optical axis
and configured to receive light that has been emitted from a light
source and backscattered by an object; a plurality of
photo-sensors; a plurality of bandpass filters, each respective
bandpass filter covering a corresponding photo-sensor of the
plurality of photo-sensors and configured to filter light received
by the respective photo-sensor, wherein each respective bandpass
filter is configured to allow a different corresponding spectral
band to pass through the respective bandpass filter; and a
plurality of beam splitters in optical communication with the lens
and the plurality of photo-sensors, wherein each respective beam
splitter in the plurality of beam splitters is configured to split
the light received by the lens into at least two optical paths, a
first beam splitter in the plurality of beam splitters is in direct
optical communication with the lens and a second beam splitter in
the plurality of beam splitters is in indirect optical
communication with the lens through the first beam splitter, and
the plurality of beam splitters collectively split the light
received by the lens into a plurality of optical paths, wherein
each respective optical path in the plurality of optical paths is
configured to direct light to a corresponding photo-sensor in the
plurality of photo-sensors through the bandpass filter
corresponding to the respective photo-sensor.
Embodiment 2
The imaging device of embodiment 1, further comprising at least one
light source having at least a first operating mode and a second
operating mode.
Embodiment 3
The imaging device of embodiment 2, wherein, in the first operating
mode, the at least one light source emits light substantially
within a first spectral range and in the second operating mode, the
at least one light source emits light substantially within a second
spectral range.
Embodiment 4
The imaging device of embodiment 3, wherein each respective
bandpass filter in the plurality of bandpass filters is configured
to allow light corresponding to either of two discrete spectral
bands to pass through the respective bandpass filter.
Embodiment 5
The imaging device of embodiment 4, wherein a first of the two
discrete spectral bands corresponds to a first spectral band that
is represented in the first spectral range and not in the second
spectral range; and a second of the two discrete spectral bands
corresponds to a second spectral band that is represented in the
second spectral range and not in the first spectral range.
Embodiment 6
The imaging device of any one of embodiments 3-5, wherein the first
spectral range is substantially non-overlapping with the second
spectral range.
Embodiment 7
The imaging device of any one of embodiments 3-6, wherein the first
spectral range is substantially contiguous with the second spectral
range.
Embodiment 8
The imaging device of embodiment 3, wherein the first spectral
range consists of 500 nm to 570 nm wavelength light, and the second
spectral ranges consists of 570 nm to 640 nm wavelength light.
Embodiment 9
The imaging device of embodiment 1, wherein the at least two
optical paths from a respective beam splitter in the plurality of
beam splitters are substantially coplanar.
Embodiment 10
The imaging device of embodiment 1, further comprising a plurality
of beam steering elements, each respective beam steering element
configured to direct light in a respective optical path to a
respective photo-sensor, of the plurality of photo-sensors,
corresponding to the respective optical path.
Embodiment 11
The imaging device of embodiment 10, wherein at least one of the
plurality of beam steering elements is configured to direct light
perpendicular to the optical axis of the lens.
Embodiment 12
The imaging device of embodiment 10, wherein each one of a first
subset of the plurality of beam steering elements is configured to
direct light in a first direction that is perpendicular to the
optical axis, and each one of a second subset of the plurality of
beam steering elements is configured to direct light in a second
direction that is perpendicular to the optical axis and opposite to
the first direction.
Embodiment 13
The imaging device of any of any of embodiments 10-12, wherein a
sensing plane of each of the plurality of photo-sensors is
substantially perpendicular to the optical axis.
Embodiment 14
The imaging device of any one of embodiments 2-8, further
comprising a polarizer in optical communication with the at least
one light source; and a polarization rotator; wherein the polarizer
is configured to: receive light from the at least one light source;
project a first portion of the light from the at least one light
source onto the object, wherein the first portion of the light is
polarized in a first manner; and project a second portion of the
light from the at least one light source onto the polarization
rotator, wherein the second portion of the light is polarized in a
second manner, other than the first manner; and wherein the
polarization rotator is configured to: rotate the polarization of
the second portion of the light from the second manner to the first
manner; and project the second portion of the light, polarized in
the first manner, onto the object.
Embodiment 15
The imaging device of embodiment 14, wherein the first manner is
p-polarization and the second manner is s-polarization.
Embodiment 16
The imaging device of embodiment 14, wherein the first manner is
s-polarization and the second manner is p-polarization.
Embodiment 17
The imaging device of any of embodiments 3-8, further comprising a
controller configured to capture a plurality of images from the
plurality of photo-sensors by performing a method including: using
the at least one light source to illuminate the object with light
falling within the first spectral range; capturing a first set of
images with the plurality of photo-sensors, wherein the first set
of images includes, for each respective photo-sensor, an image
corresponding to a first spectral band transmitted by the
respective bandpass filter, wherein the light falling within the
first spectral range includes light falling within the first
spectral band of each bandpass filter; using the at least one light
source to illuminate the object with light falling within the
second spectral range; and capturing a second set of images with
the plurality of photo-sensors, wherein the second set of images
includes, for each respective photo-sensor, an image corresponding
to a second spectral band transmitted by the respective bandpass
filter, wherein the light falling within the second spectral range
includes light falling within the second spectral band of each
bandpass filter.
Embodiment 18
The imaging device of any of embodiments 1-17, wherein the lens has
a fixed focus distance, the imaging device further comprising: a
first projector configured to project a first portion of a shape
onto the object; and a second projector configured to project a
second portion of the shape onto the object; wherein the first
portion of the shape and the second portion of the shape are
configured to converge to form the shape when the lens is
positioned at a predetermined distance from the object, the
predetermined distance corresponding to the focus distance of the
lens.
Embodiment 19
The imaging device of embodiment 18, wherein the shape indicates a
portion of the object that will be imaged by the plurality of
photo-sensors when an image is captured with the imaging
device.
Embodiment 20
The imaging device of embodiment 19, wherein the shape is selected
from the group consisting of: a rectangle; a square; a circle; and
an oval.
Embodiment 21
The imaging device of any of embodiments 18-20, wherein the first
portion of the shape is a first pair of lines forming a right
angle, and the second portion of the shape is a second pair of
lines forming a right angle, wherein, the first portion of the
shape and the second portion of the shape are configured to form a
rectangle on the object when the imaging device is positioned at a
predetermined distance from the object.
Embodiment 22
The imaging device of any of embodiments 1-21, wherein each of the
plurality of beam splitters exhibits a ratio of light transmission
to light reflection of about 50:50.
Embodiment 23
The imaging device of embodiment 22, wherein at least one of the
beam splitters in the plurality of beam splitters is a dichroic
beam splitter.
Embodiment 24
The imaging device of embodiment 23, wherein at least the first
beam splitter is a dichroic beam splitter.
Embodiment 25
The imaging device of embodiment 1, further comprising: at least
one light source having at least a first operating mode and a
second operating mode, and wherein each of the plurality of beam
splitters exhibits a ratio of light transmission to light
reflection of about 50:50, at least one of the beam splitters in
the plurality of beam splitters is a dichroic beam splitter, in the
first operating mode, the at least one light source emits light
substantially within a first spectral range that includes at least
two discontinuous spectral sub-ranges; and in the second operating
mode, the at least one light source emits light substantially
within a second spectral range.
Embodiment 26
The imaging device of embodiment 25, wherein the first beam
splitter is configured to transmit light falling within a third
spectral range and reflect light falling within a fourth spectral
range.
Embodiment 27
The imaging device of embodiment 26, wherein the plurality of beam
splitters includes the first beam splitter, the second beam
splitter, and a third beam splitter.
Embodiment 28
The imaging device of embodiment 27, wherein the light falling
within the third spectral range is transmitted toward the second
beam splitter, and the light falling within the fourth spectral
range is reflected toward the third beam splitter.
Embodiment 29
The imaging device of embodiment 28, wherein the second and the
third beam splitters are wavelength-independent beam splitters.
Embodiment 30
The imaging device of any of embodiments 25-29, wherein the at
least two discontinuous spectral sub-ranges of the first spectral
range include: a first spectral sub-range of about 450-550 nm; and
a second spectral sub-range of about 615-650 nm; and the second
spectral range is about 550-615 nm.
Embodiment 31
The imaging device of any of embodiments 26-30, wherein the third
spectral range is about 585-650 nm; and the fourth spectral range
is about 450-585 nm.
Embodiment 32
The imaging device of any one of embodiments 26-31, wherein the
third spectral range includes light falling within both the first
and the second spectral ranges; and the fourth spectral range
includes light falling within both the first and the second
spectral ranges.
Embodiment 33
The imaging device of any one of embodiments 24-32, wherein the
first beam splitter is a plate dichroic beam splitter or a block
dichroic beam splitter.
Embodiment 34
The imaging device of embodiment 23, wherein the first beam
splitter, the second beam splitter, and the third beam splitter are
dichroic beam splitters.
Embodiment 35
The imaging device of embodiment 34, wherein: in the first
operating mode, the at least one light source emits light
substantially within a first spectral range that includes at least
two discontinuous spectral sub-ranges; and in the second operating
mode, the at least one light source emits light substantially
within a second spectral range.
Embodiment 36
The imaging device of embodiment 35, wherein the first beam
splitter is configured to transmit light falling within a third
spectral range that includes at least two discontinuous spectral
sub-ranges and reflect light falling within a fourth spectral range
that includes at least two discontinuous spectral sub-ranges.
Embodiment 37
The imaging device of embodiment 36, wherein the plurality of beam
splitters includes the first beam splitter, the second beam
splitter, and a third beam splitter.
Embodiment 38
The imaging device of embodiment 37, wherein the light falling
within the third spectral range is transmitted toward the second
beam splitter, and the light falling within the fourth spectral
range is reflected toward the third beam splitter.
Embodiment 39
The imaging device of embodiment 38, wherein the second beam
splitter is configured to reflect light falling within a fifth
spectral range that includes at least two discontinuous spectral
sub-ranges and transmit light not falling within either of the at
least two discontinuous spectral sub-ranges of the fifth spectral
sub-range.
Embodiment 40
The imaging device of embodiment 38 or embodiment 39, wherein the
third beam splitter is configured to reflect light falling within a
sixth spectral range that includes at least two discontinuous
spectral sub-ranges and transmit light not falling within either of
the at least two discontinuous spectral sub-ranges of the sixth
spectral sub-range.
Embodiment 41
The imaging device of any of embodiments 35-40, wherein: the at
least two discontinuous spectral sub-ranges of the first spectral
range include: a first spectral sub-range of about 450-530 nm; and
a second spectral sub-range of about 600-650 nm; and the second
spectral range is about 530-600 nm.
Embodiment 42
The imaging device of any of embodiments 36-41, wherein: the at
least two discontinuous spectral sub-ranges of the third spectral
range include: a third spectral sub-range of about 570-600 nm; and
a fourth spectral sub-range of about 615-650 nm; and the at least
two discontinuous spectral sub-ranges of the fourth spectral range
include: a fifth spectral sub-range of about 450-570 nm; and a
sixth spectral sub-range of about 600-615 nm.
Embodiment 43
The imaging device of any of embodiments 39-42, wherein: the at
least two discontinuous spectral sub-ranges of the fifth spectral
range include: a seventh spectral sub-range of about 585-595 nm;
and an eighth spectral sub-range of about 615-625 nm.
Embodiment 44
The imaging device of any of embodiments 40-43, wherein: the at
least two discontinuous spectral sub-ranges of the sixth spectral
range include: a ninth spectral sub-range of about 515-525 nm; and
a tenth spectral sub-range of about 555-565 nm.
Embodiment 45
The imaging device of any of embodiments 34-44, wherein the first
beam splitter, the second beam splitter, and the third beam
splitter are each either a plate dichroic beam splitter or a block
dichroic beam splitter.
Embodiment 46
The imaging device of any of embodiments 3-7, wherein the at least
one light source includes a first set of light emitting diodes
(LEDs) and a second set of LEDs; each LED of the first set of LEDs
transmits light through a first bandpass filter of the plurality of
bandpass filters that is configured to block light falling outside
the first spectral range and transmit light falling within the
first spectral range; and each LED of the second set of LEDs
transmits light through a second bandpass filter of the plurality
of bandpass filters that is configured to block light falling
outside the second spectral range and transmit light falling within
the second spectral range.
Embodiment 47
The imaging device of embodiment 46, wherein the first set of LEDs
are in a first lighting assembly and the second LEDs are in a
second lighting assembly separate from the first lighting
assembly.
Embodiment 48
The imaging device of embodiment 46, wherein the first set of LEDs
and the second set of LEDs are in a common lighting assembly.
Embodiment 49
An optical assembly for an imaging device, comprising: a lens
disposed along an optical axis; an optical path assembly configured
to receive light from the lens; a first circuit board positioned on
a first side of the optical path assembly; and a second circuit
board positioned on a second side of the optical path assembly
opposite to the first side, wherein the second circuit board is
substantially parallel with the first circuit board; wherein the
optical path assembly includes: a first beam splitter configured to
split light received from the lens into a first optical path and a
second optical path, wherein the first optical path is
substantially collinear with the optical axis, and the second
optical path is substantially perpendicular to the optical axis; a
second beam splitter configured split light from the first optical
path into a third optical path and a fourth optical path, wherein
the third optical path is substantially collinear with the first
optical path, and the fourth optical path is substantially
perpendicular to the optical axis; a third beam splitter configured
to split light from the second optical path into a fifth optical
path and a sixth optical path, wherein the fifth optical path is
substantially collinear with the second optical path, and the sixth
optical path is substantially perpendicular to the second optical
path; a first beam steering element configured to deflect light
from the third optical path perpendicular to the third optical path
and onto a first photo-sensor coupled to the first circuit board; a
second beam steering element configured to deflect light from the
fourth optical path perpendicular to the fourth optical path and
onto a second photo-sensor coupled to the second circuit board; a
third beam steering element configured to deflect light from the
fifth optical path perpendicular to the fifth optical path and onto
a third photo-sensor coupled to the first circuit board; and a
fourth beam steering element configured to deflect light from the
sixth optical path perpendicular to the sixth optical path and onto
a fourth photo-sensor coupled to the second circuit board.
Embodiment 50
The optical assembly of embodiment 49, further comprising a
plurality of bandpass filters, the plurality of bandpass filters
comprising: a first bandpass filter positioned in the third optical
path between the first beam splitter and the first photo-sensor; a
second bandpass filter positioned in the fourth optical path
between the second beam splitter and the second photo-sensor; a
third bandpass filter positioned in the fifth optical path between
the third beam splitter and the third photo-sensor; and a fourth
bandpass filter positioned in the sixth optical path between the
fourth beam splitter and the fourth photo-sensor, wherein each
respective bandpass filter in the plurality of bandpass filters is
configured to allow a different respective spectral band to pass
through the respective bandpass filter.
Embodiment 51
The optical assembly of embodiment 50, wherein at least one
respective bandpass filter in the plurality of bandpass filters is
a dual bandpass filter.
Embodiment 52
The optical assembly of any one of embodiments 49-51, further
comprising a polarizing filter disposed along the optical axis.
Embodiment 53
The optical assembly of embodiment 52, wherein the polarizing
filter is adjacent to the lens and before the first beam splitter
along the optical axis.
Embodiment 54
The optical assembly of any one of embodiments 49-53, wherein the
first beam steering element is a mirror or prism.
Embodiment 55
The optical assembly of any of embodiments 49-53, wherein the first
beam steering element is a folding prism.
Embodiment 56
The optical assembly of any one of embodiments 49-55, wherein each
respective beam splitter and each respective beam steering element
is oriented along substantially the same plane.
Embodiment 57
The optical assembly of any of embodiments 49-56, wherein each
respective photo-sensor is flexibly coupled to its corresponding
circuit board.
Embodiment 58
The optical assembly of any one of embodiments 49-57, wherein the
first beam splitter, the second beam splitter, and the third beam
splitter each exhibits a ratio of light transmission to light
reflection of about 50:50.
Embodiment 59
The optical assembly of any one of embodiments 49-57, wherein at
least the first beam splitter is a dichroic beam splitter.
Embodiment 60
The optical assembly of embodiment 59, wherein the first beam
splitter is configured to transmit light falling within a first
spectral range and reflect light falling within a second spectral
range.
Embodiment 61
The optical assembly of embodiment 60, wherein the light falling
within the first spectral range is transmitted toward the second
beam splitter, and the light falling within the second spectral
range is reflected toward the third beam splitter.
Embodiment 62
The optical assembly of embodiment 61, wherein the second and the
third beam splitters are wavelength-independent beam splitters.
Embodiment 63
The optical assembly of any one of embodiments 49-57, wherein the
first beam splitter, the second beam splitter, and the third beam
splitter are dichroic beam splitters.
Embodiment 64
The optical assembly of embodiment 63, wherein the first beam
splitter is configured to transmit light falling within a first
spectral range that includes at least two discontinuous spectral
sub-ranges and reflect light falling within a second spectral range
that includes at least two discontinuous spectral sub-ranges.
Embodiment 65
The optical assembly of any one of embodiments 63-64, wherein the
second beam splitter is configured to reflect light falling within
a third spectral range that includes at least two discontinuous
spectral sub-ranges and transmit light not falling within either of
the at least two discontinuous spectral sub-ranges of the third
spectral sub-range.
Embodiment 66
The optical assembly of any one of embodiments 63-65, wherein the
third beam splitter is configured to reflect light falling within a
fourth spectral range that includes at least two discontinuous
spectral sub-ranges and transmit light not falling within either of
the at least two discontinuous spectral sub-ranges of the fourth
spectral sub-range.
Embodiment 67
A lighting assembly for an imaging device, comprising: at least one
light source; a polarizer in optical communication with the at
least one light source; and a polarization rotator; wherein the
polarizer is configured to: receive light from the at least one
light source; project a first portion of the light from the at
least one light source onto an object, wherein the first portion of
the light exhibits a first type of polarization; and project a
second portion of the light from the at least one light source onto
the polarization rotator, wherein the second portion of the light
exhibits a second type of polarization; and wherein the
polarization rotator is configured to: rotate the polarization of
the second portion of the light from the second type of
polarization to the first type of polarization; and project the
light of the first type of polarization onto the object.
Embodiment 68
The lighting assembly of embodiment 67, wherein the first type of
polarization is p-polarization and the second type of polarization
is s-polarization.
Embodiment 69
The lighting assembly of embodiment 67, wherein the first type of
polarization is s-polarization and the second type of polarization
is p-polarization.
Embodiment 70
The lighting assembly of any of embodiments 67-69, wherein the at
least one light source is one or more light emitting diode
(LED).
Embodiment 71
The lighting assembly of any of embodiments 67-70, wherein the at
least one light source has two or more operating modes, each
respective operating mode in the two or more operation modes
includes emission of a discrete spectral range of light, wherein
none of the respective spectral ranges of light corresponding to an
operating mode completely overlaps with any other respective
spectral range of light corresponding to a different operating
mode.
Embodiment 72
The lighting assembly of any of embodiments 67-71, wherein at least
95% of all of the light received by the polarizer from the at least
one light source is illuminated onto the object.
Embodiment 73
A method for capturing a hyper-spectral/multispectral image of an
object, comprising: at an imaging system comprising: at least one
light source; a lens configured to receive light that has been
emitted from the at least one light source and backscattered by an
object; a plurality of photo-sensors; and a plurality of bandpass
filters, each respective bandpass filter in the plurality of
bandpass filters covering a respective photo-sensor of the
plurality of photo sensors and configured to filter light received
by the respective photo-sensor, wherein each respective bandpass
filter is configured to allow a different respective spectral band
to pass through the respective bandpass filter; illuminating the
object with the at least one light source according to a first mode
of operation of the at least one light source; capturing a first
plurality of images, each of the first plurality of images being
captured by a respective one of the plurality of photo-sensors,
wherein each respective image of the first plurality of images
includes light having a different respective spectral band.
Embodiment 74
The method of embodiment 73, wherein each of the plurality of
bandpass filters is configured to allow light corresponding to
either of two discrete spectral bands to pass through the filter,
the method further comprising: after capturing the first plurality
of images: illuminating the object with the at least one light
source according to a second mode of operation of the at least one
light source; capturing a second plurality of images, each of the
second plurality of images being captured by a respective one of
the plurality of photo-sensors, wherein: each respective image of
the second plurality of images includes light having a different
respective spectral band; and the spectral bands captured by the
second plurality of images are different than the spectral bands
captured by the first plurality of images.
Embodiment 75
The method of any of embodiments 73-74, wherein the at least one
light source comprises a plurality of light emitting diodes
(LEDs).
Embodiment 76
The method of embodiment 75, wherein a first wavelength optical
filter is disposed along an illumination optical path between a
first subset of LEDs in the plurality of LEDs and the object; and a
second wavelength optical filter is disposed along an illumination
optical path between a second subset of LEDs in the plurality of
LEDs and the object, wherein the first wavelength optical filter
and the second wavelength optical filter are configured to allow
light corresponding to different spectral bands to pass through the
respective filters.
Embodiment 77
The method of embodiment 76, wherein the plurality of LEDs comprise
white light-emitting LEDs.
Embodiment 78
The method of embodiment 75, wherein the plurality of LEDs
comprises a first subset of LEDs configured to emit light
corresponding to a first spectral band of light and a second subset
of LEDs configured to emit light corresponding to a second spectral
band of light: illuminating the object with the at least one light
source according to a first mode of operation consisting of
illuminating the object with light emitted from the first subset of
LEDs; and illuminating the object with the at least one light
source according to a second mode of operation consisting of
illuminating the object with light emitted from the second subset
of LEDs, wherein the wavelengths of the first spectral band of
light and the wavelengths of the second spectral band of light do
not completely overlap.
Embodiment 79
An imaging device, comprising: at least one light source having at
least two operating modes; a lens disposed along an optical axis
and configured to receive light that has been emitted from the at
least one light source and backscattered by an object; a plurality
of photo-sensors; a plurality of bandpass filters, each respective
bandpass filter covering a corresponding photo-sensor of the
plurality of photo-sensors and configured to filter light received
by the corresponding photo-sensor, wherein each respective bandpass
filter is configured to allow a different respective spectral band
to pass through the respective bandpass filter; and one or more
beam splitters in optical communication with the lens and the
plurality of photo-sensors, wherein each respective beam splitter
is configured to split the light received by the lens into a
plurality of optical paths, each optical path configured to direct
light to a corresponding photo-sensor of the plurality of
photo-sensors through the bandpass filter corresponding to the
corresponding photo-sensor.
It will also be understood that, although the terms "first,"
"second," etc. may be used herein to describe various elements,
these elements should not be limited by these terms. These terms
are only used to distinguish one element from another. For example,
a first contact could be termed a second contact, and, similarly, a
second contact could be termed a first contact, which changing the
meaning of the description, so long as all occurrences of the
"first contact" are renamed consistently and all occurrences of the
second contact are renamed consistently. The first contact and the
second contact are both contacts, but they are not the same
contact.
The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the claims. As used in the description of the embodiments and the
appended claims, the singular forms "a", "an" and "the" are
intended to include the plural forms as well, unless the context
clearly indicates otherwise. It will also be understood that the
term "and/or" as used herein refers to and encompasses any and all
possible combinations of one or more of the associated listed
items. It will be further understood that the terms "comprises"
and/or "comprising," when used in this specification, specify the
presence of stated features, integers, steps, operations, elements,
and/or components, but do not preclude the presence or addition of
one or more other features, integers, steps, operations, elements,
components, and/or groups thereof.
As used herein, the term "if" may be construed to mean "when" or
"upon" or "in response to determining" or "in accordance with a
determination" or "in response to detecting," that a stated
condition precedent is true, depending on the context. Similarly,
the phrase "if it is determined [that a stated condition precedent
is true]" or "if [a stated condition precedent is true]" or "when
[a stated condition precedent is true]" may be construed to mean
"upon determining" or "in response to determining" or "in
accordance with a determination" or "upon detecting" or "in
response to detecting" that the stated condition precedent is true,
depending on the context.
The foregoing description, for purpose of explanation, has been
described with reference to specific embodiments. However, the
illustrative discussions above are not intended to be exhaustive or
to limit the invention to the precise forms disclosed. Many
modifications and variations are possible in view of the above
teachings. The embodiments were chosen and described in order to
best explain the principles of the invention and its practical
applications, to thereby enable others skilled in the art to best
utilize the invention and various embodiments with various
modifications as are suited to the particular use contemplated.
* * * * *